Flow configuration for electrolytic cells, electrolytic cells, electrolytic installations, methods of operation and methods of manufacture - Patent Application 20070122997

Abstract

Disclosed is a flow configuration (100) for an electrolytic cell, comprising first and second porous walls (110) and (120) corresponding to first and second electrodes of the electrolytic cell, an inlet chamber (102) disposed between the first and second porous walls and configured to receive a fluid through an inlet, and first and second outlet chambers (130) and (140) for holding respective fluid reaction products of the electrolysis. One or each of the porous walls comprises a body (116) and a plurality of porous regions (117) extending through the body at discrete locations to allow fluid to flow from the inlet chamber to a respective outlet chamber, each porous region defining a respective network of flow paths through the body. Electrolytic cell and electrolysis equipment, methods of operation, and methods of manufacture are also disclosed.

Description

[Technical Field]

[0001] The present disclosure relates to flow configurations for electrolytic cells, electrolytic cells, electrolysis installations, methods of operation and methods of manufacture for such electrolytic cells or installations. In particular, but not exclusively, the disclosure relates to such systems and methods for carrying out continuous electrolysis at supercritical conditions, in particular the electrolysis of water and aqueous electrolyte solutions. [Background technology]

[0002] One application of electrolysis is the production of hydrogen for energy storage. Electricity can be used to separate hydrogen and oxygen from water. The stored hydrogen and oxygen can be recombined in a fuel cell to produce electricity. Meanwhile, the hydrogen (and oxygen) can be stored and transported. With improvements in the efficiency of electrolysis and fuel cell technology, hydrogen energy storage has been proposed as a solution to many energy storage problems, particularly the storage of energy from renewable sources.

[0003] The efficiency of electrolysis depends on losses inherent in the design of the electrolysis cell. Such losses can be thought of as giving the electrolysis cell an overpotential, which represents the cell requiring more energy than theoretically thermodynamically required to continue the electrolysis reaction.

[0004] Overpotentials can arise from several different factors. For example, the predominate method of water electrolysis relies on the use of a polymer electrolyte membrane (PEM electrolysis) to separate the cathode and anode to prevent mixing of the hydrogen and oxygen reaction products while allowing ion transport. However, the presence of the PEM membrane introduces overpotentials into the system. Electrolysis cell designs that do not use PEM membranes are being considered, but such designs face challenges in separating the reaction products and keeping them separate (e.g., oxygen and hydrogen) while allowing efficient ion exchange for the electric field (i.e., minimizing overpotentials).

[0005] Further overvoltages are introduced by the formation of reaction product bubbles (e.g., hydrogen and oxygen bubbles) that reside on and block the electrode surfaces, and by the presence of electrolyte (e.g., in the electrolyte solution surrounding the electrodes).

[0006] It is desirable to reduce the overpotential associated with electrolysis.

[0007] To avoid the use of PEM membranes, it has been proposed to use electrolytic cells with porous walls. WO 2022 / 106874 proposes using a porous wall to divide a central first fluid channel 7 that receives fluid from outer second and third channels 9 and 11, with electrodes 3, 5 disposed within the second and third channels 9 and 11. The porous wall is made porous by having sloping channels connecting the first fluid channel 7 with the second and third channels 9 and 11, respectively, with the sloping channels having opening widths or diameters of 50 μm to 200 μm. Summary of the Invention

[0008] According to a first aspect, there is provided a flow arrangement for an electrolytic cell, comprising: a first porous wall and a second porous wall corresponding to the first electrode and the second electrode of the electrolytic cell; an inlet chamber disposed between the first porous wall and the second porous wall and configured to receive a fluid through the inlet; a first outlet chamber and a second outlet chamber for retaining respective fluid reaction products of the electrolysis, the first and second outlet chambers being separated from the inlet chamber by a first porous wall and a second porous wall, respectively; Equipped with One or each of the first porous wall and the second porous wall has a discontinuous porous structure, and the or each porous wall having a discontinuous porous structure comprises: a body having an inlet side adjacent the inlet chambers and an outlet side adjacent each of the outlet chambers, the body being elongate along a longitudinal direction and having a thickness direction from the inlet side to the outlet side; a plurality of porous regions extending through the body at discrete locations to allow fluid to flow from the inlet chamber to respective outlet chambers; A flow configuration is disclosed in which each porous region defines a respective network of flow channels through the body.

[0009] For the or each porous wall having a discontinuous porous structure, each porous region may be elongate along a path through the body having a longitudinal component.

[0010] For the or each porous wall having a discontinuous porous structure, each porous region may be elongate along a path through the body that defines a path angle of between 20° and 80° with respect to the longitudinal direction.

[0011] The path angle may be between 25° and 75°, for example, between 30° and 70°, between 35° and 70°, between 40° and 70°, for example, between 50° and 70°.

[0012] The term "elongate" refers to the property that a porous region is long relative to its width, such that the direction along which the porous region is elongate defines a path (having a longitudinal component). A longitudinal component is a non-zero component of a path that corresponds to (e.g., is parallel to) the longitudinal direction of the body. It should be appreciated that an elongate object (e.g., a structure, region, member) has a single elongate path (which may be a bidirectional path). Thus, a path along which the porous region has an extent but that does not correspond to the path along which the porous region is elongate is not a path that meets the above definition. The path may be linear or substantially linear. The path may also be curved.

[0013] Definitions regarding the elongation and / or orientation (e.g., angle of inclination) of each porous region may be expressed interchangeably with respect to the porous region itself or the boundary of the porous region where it interfaces with the body. In particular, for each porous region as defined above, there exists such a boundary that is elongated along a path through the body having a longitudinal component (e.g., the same path as that of the porous region). Each of the above definitions regarding the path of a porous region is equally and interchangeably applicable to a boundary. Each boundary may surround the respective porous region to form a closed boundary with open ends corresponding to the inlet and outlet sides of the body. The path or boundary of a porous region may be defined by reference to a centerline path through the porous region or boundary (respectively), which may be a path passing through the centroids of multiple cross sections of the porous region or boundary (respectively) at successive locations along the thickness direction (also understood or referred to as a centroid axis).

[0014] The flow configuration may be that of a continuous electrolysis cell (i.e., a cell configured to simultaneously receive an inlet stream of electrolyte liquid and discharge an outlet stream of fluid reaction products produced by each electrolysis reaction). The or each porous-walled body may be defined as having an anisotropic porous structure provided by the arrangement of porous regions within the body (i.e., by the porous regions being discretely located and elongated along a path having a longitudinal component, thereby providing non-uniform flow through the body as a whole). The porous region itself may be defined as having an isotropic structure, for example, as provided by a generally uniform distribution of porous media. The porous media may be isotropic in that it is generally uniformly distributed within the porous region, with only the boundaries of the porous region imparting anisotropy to the porous wall.

[0015] The flow configuration may be configured for the or each porous wall having a discontinuous porous structure to be installed in an installed orientation in that each of the respective plurality of porous regions has an elongate path along it having an upward component toward the outlet chamber, and each porous region may thus be configured to inhibit backflow from the respective outlet chamber to the inlet chamber when buoyancy-driven flow through the porous region having an upward component prevails.

[0016] The flow configuration may be configured such that when the or each porous wall having a discontinuous porous structure is vertically upward, each of the respective plurality of porous regions is elongated along a path toward a respective outlet chamber with an upward component.

[0017] The thickness direction can be the direction corresponding to the shortest distance from the inlet side to the outlet side. The thickness direction can be perpendicular to the longitudinal direction of each porous wall. The porous walls can each be elongate relative to a common longitudinal direction (i.e., they can each be elongate along a parallel direction) and have a respective thickness direction perpendicular to the common longitudinal direction.

[0018] The or each porous wall may be axisymmetric about its longitudinal direction, such that the thickness direction at any angular location about the longitudinal direction is the local thickness direction corresponding to the radial direction about the longitudinal direction. When both porous walls are axisymmetric, they may also be coaxial with each other. The longitudinal direction may pass through the centroid of the cross section of the or each porous wall.

[0019] In other aspects, the flow configuration may be implemented with one or more non-axisymmetric porous walls, such as planar porous walls that extend linearly along both the lateral and longitudinal directions. The extent of the porous wall along the longitudinal direction may be relatively greater than the extent along the lateral direction, so that it is elongated along the longitudinal direction.

[0020] Both the first porous wall and the second porous wall have a discontinuous porous structure, and at least one characteristic of the discontinuous porous structure selected from the group consisting of:

[0021] the porosity of each porous wall, with an associated minimum offset of 0.01; The macroporosity of each porous wall, defined as the porosity of the body of the porous wall in the absence of porous regions for each porous wall, with an associated minimum offset of 0.01; the microporosity of each porous wall, defined as the porosity of the porous region for each porous wall, with an associated minimum offset of 0.05; The pitch at which each porous region is spaced apart, with a minimum offset of 10% for each pitch of the porous walls; the average cross-sectional area of ​​each porous region, each cross-sectional area being determined by dividing the volume of the porous region by the extent of the porous region along the thickness direction, with an associated minimum offset of 10%; the average diameter of each porous region when each porous region has a circular cross section perpendicular to the path along which the porous region is elongated, with an associated minimum offset of 10%; a path angle of each porous region, determined as the angle between the path along which the porous region extends and its respective longitudinal direction, with an associated minimum offset of 5°; and The thickness of the porous wall along each thickness direction, with an associated minimum offset of 10% for the thinnest porous wall.

[0022] The minimum offset, as defined above, is the smallest amount that the respective values ​​of the parameters differ, eg, they may differ by at least this amount (and therefore may differ by more than this amount).

[0023] The minimum offset associated with the porosity of each porous wall may be at least 0.01, e.g., at least 0.02, at least 0.05, at least 0.1, at least 0.2, or at least 0.3. The porosity of each porous wall may differ by an offset of 0.01 to 0.5, e.g., 0.01 to 0.3, 0.02 to 0.3, 0.1 to 0.3, 0.2 to 0.3.

[0024] The minimum offset associated with the macroporosity of each porous wall may be at least 0.01, e.g., at least 0.02, at least 0.05, at least 0.1, at least 0.2, or at least 0.3. The porosity of each porous wall may differ by an offset of 0.01 to 0.5, e.g., 0.01 to 0.3, 0.02 to 0.3, 0.1 to 0.3, 0.2 to 0.3.

[0025] The minimum offset associated with the microporosity of each porous wall may be at least 0.05, e.g., at least 0.1, at least 0.2, at least 0.3, or at least 0.5. The porosity of each porous wall may differ by an offset of 0.05 to 0.8, e.g., 0.1 to 0.8, 0.2 to 0.8, 0.3 to 0.8, 0.5 to 0.8.

[0026] Macroporosity as defined above may alternatively be referred to as the primary porosity of the or each porous wall. Macroporosity as defined above may alternatively be referred to as the secondary porosity of the or each porous wall.

[0027] The minimum offset associated with the average cross-sectional area of ​​each porous region may be at least 10%, e.g., at least 20%, at least 30%, at least 50%, or at least 100%. The average cross-sectional areas may differ by an offset of 10% to 200%, e.g., 10% to 200%, 20% to 200%, 30% to 200%, 50% to 200%, or 100% to 200%. The average cross-sectional areas may differ by an offset of 10% to 100%, e.g., 10% to 100%, 20% to 100%, 30% to 100%, or 50% to 100%.

[0028] The minimum offset associated with the average diameter of each porous region may be at least 10%, e.g., at least 20%, at least 30%, at least 50%, or at least 100%. The average diameters may differ by an offset of 10% to 200%, e.g., 10% to 200%, 20% to 200%, 30% to 200%, 50% to 200%, or 100% to 200%. The average diameters may differ by an offset of 10% to 100%, e.g., 10% to 100%, 20% to 100%, 30% to 100%, or 50% to 100%.

[0029] The minimum offset associated with the path angle of each porous region may be 5° or more, e.g., 10° or more, 15° or more, 20° or more. The path angles may differ by an offset between 5° and 60°, e.g., between 10° and 60°, between 15° and 60°, between 20° and 60°, between 5° and 40°, between 10° and 40°, between 15° and 40°, between 20° and 40°, between 5° and 20°, or between 10° and 20°.

[0030] The minimum offset associated with the thickness of each porous region may be at least 10%, e.g., at least 20%, at least 30%, at least 50%, or at least 100%. The thicknesses may differ by an offset of 10% to 200%, e.g., 10% to 200%, 20% to 200%, 30% to 200%, 50% to 200%, or 100% to 200%. The average cross-sectional areas may differ by an offset of 10% to 100%, e.g., 10% to 100%, 20% to 100%, 30% to 100%, or 50% to 100%.

[0031] When the parameters relate to averages, they may be defined as the number-weighted average of the respective plurality of porous regions.

[0032] Porosity as defined herein is the open porosity of each component or structure.

[0033] The porosity of a porous wall is the total porosity of the porous wall. As described elsewhere herein, porosity shall be evaluated over the longitudinal extent of the porous wall that is configured to be porous (excluding non-porous proximal or distal locations, e.g., for electrical connections).

[0034] The microporosity of a porous wall relates only to the porosity of the porous region of the porous wall. Thus, the microporosity of a porous wall can relate to the porosity of the porous medium located within the porous region. The microporosity of a porous medium (e.g., when a sample of the porous medium is isolated or manufactured separately from the porous wall), and therefore the microporosity of the porous wall, can be measured directly by mercury porosimetry according to ASTM standards D4284 and D6761 using an AutoPore V device (available from Micromeritics Instrument Corporation, USA).

[0035] The macroporosity of each porous wall relates to the porosity of the body of the porous wall considered alone (e.g., the entire porous area is considered to be open, i.e., does not contain any porous media). The macroporosity of a porous wall can be calculated by reference to the design and / or measured dimensions of the porous wall (including the dimensions of the open area). Alternatively, if the open area is not or has not yet been filled with porous media, the macroporosity of the porous wall can be measured directly by mercury porosimetry according to ASTM standards D4284 and D6761 using an AutoPore V device (available from Micromeritics Instrument Corporation, USA).

[0036] The total porosity of the porous wall can be determined as the product of the macroporosity and the microporosity. Alternatively, if the open area of ​​the porous wall already contains a porous medium, the total porosity of the porous wall can be measured directly by mercury porosimetry according to ASTM standards D4284 and D6761 using an AutoPore V device (available from Micromeritics Instrument Corporation, USA). The microporosity of the porous wall can also be determined by dividing the measured total porosity of the porous wall by the measured or calculated macroporosity of the porous wall (for example, without isolating the porous medium from the porous wall).

[0037] The pitch may be uniform or may be determined by reference to the nearest interval in a non-uniform distribution of porous regions. The path angle of each porous region may be uniform or may be determined as the average of the angles of each porous region.

[0038] The diameter of the porous region can be determined as the average diameter of the porous region measured at the ends of the porous region on the inlet and outlet sides of each wall. Considering that the porous regions may have a longitudinal extent, they may present a substantially elliptical profile on the inlet and outlet sides, in which case the diameter would be measured as the circumferential extent of each end of the porous region.

[0039] The path angle between the path along which the porous region extends and the longitudinal direction can be determined as the angle between the path along which the boundary of the porous region extends and the longitudinal direction, and can be evaluated in a plane containing the longitudinal direction and the local thickness direction (i.e., the plane in which these directions lie). Similarly, the angle between the path along which the porous region extends and each longitudinal direction can be determined as the angle between the path along which the boundary of the porous region extends and the longitudinal direction, and can be evaluated in a respective plane containing the longitudinal direction and each local thickness direction. The local thickness direction is the thickness direction local to each porous region. For example, for an annular porous wall, the thickness direction can vary around the porous wall and correspond to the radial direction of the porous wall. The angle of inclination of each porous region can be uniform or can be determined as the average of the angles of each boundary of the porous region.

[0040] The term "pitch," as used above, takes its ordinary meaning in the art and refers to the distance between the centers of the porous regions. The present disclosure assumes that when the first and second porous walls are non-planar (e.g., annular), pitch is still determined by reference to the absolute distance between the centers of the porous regions, but when annular (e.g., when the porous regions terminate radially inward of the respective porous walls or when the radially inward has openings to the respective porous regions), pitch is evaluated at the radially inward of the respective porous walls. Thus, for concentric and annular first and second porous walls, equal angular distributions of porous regions will nevertheless correspond to different pitches.

[0041] For the or each porous wall having a discontinuous porous structure, the porous regions can each have a porosity (e.g., microporosity) of 0.2-0.9, e.g., 0.2-0.8, or 0.3-0.8, or 0.5-0.8, or 0.6-0.8, or 0.3-0.7. The porosity of the porous regions can be determined by mercury porosimetry according to ASTM standards D4284 and D6761, as described elsewhere herein (e.g., using an AutoPore V device (available from Micromeritics Instrument Corporation, USA)).

[0042] The or each porous wall having a discontinuous porous structure may have a porosity (e.g., total porosity) of 0.03 to 0.5, e.g., 0.03 to 0.3, or 0.03 to 0.2, or 0.05 to 0.15, or 0.05 to 0.1. The porosity of the porous wall may be determined by mercury porosimetry according to ASTM standards D4284 and D6761, as described elsewhere herein (e.g., using an AutoPore V device (available from Micromeritics Instrument Corporation, USA)).

[0043] The or each porous wall having a discontinuous porous structure has a porous content of 1% to 20%, for example, 2% to 20%, or 3% to 20%, or 4% to 20%, or 5% to 20%, or 6% to 20%, or 7% to 20%, or 8% to 20%, or 9% to 20%, or 10% to 20%, or 1% to 19%, or 2% to 19%, or 3% to 19%, or 4% to 19%, or 5% to 19%, or 6% to 19%, or 7% to 19%, or 8% to 19%, or 9% to 19%, or 10% to 19%, or 1% to 18%, or 2% to 18%, or 3% to 18%, or 4% to 18%, or 5% to 18%, or 6% to 18%, or 7% to 18%, or 8% to 18%, or 9% to 18%, or 10% to 18%, or 1% to 17%, or 2% to 17%, or 3% to 17%, or 4% to 17%, or 5% to 17%, or 6% to 17%, or 7% to 17%, or 8% to 17%, or 9% to 17%, or 10% to 17%, or 1% to 16%, or 2% to 16%, or 3% to 16%, or 4% to 16%, or 5% to 16%, or 6% to 16%, or 7% to 1 6%, or 8% to 16%, or 9% to 16%, or 10% to 16%, or 1% to 15%, or 2% to 15%, or 3% to 15%, or 4% to 15%, or 5% to 15%, or 6% to 15%, or 7% to 15%, or 8% to 15%, or 9% to 15%, or 10% to 15%, or 1% to 14%, or 2% to 14%, or 3% to 14%, or 4% to 14%, or 5% to 14%, or 6% to 14%, or 7% to 14%, or 8% to 14%, or 9% to 14%, or 10% to 14%, or 1% to 13%, or 2% to 13%, or 3% to 13%, or 4% to 13%, or 5% to 13%, or 6% to 13%, or 7% to 13%, or 8% to 13%, or 9% to 13%, or 10% to 13%, or 1% to 12%, or 2% to 12%, or 3% to 12%, or 4% to 12%, or 5% to 12%, or 6% to 12%, or 7% to 12%, or 8% to 12%, or 9% to 12%, or 10% to 12%, or 1% to 11%, or 2% to 11%, or 3% to 11%, or 4% to 11%, or 5% to 11%, or 6% to 11%,or 7% to 11%, or 8% to 11%, or 9% to 11%, or 10% to 11%, or 1% to 10%, or 2% to 10%, or 3% to 10%, or 4% to 10%, or 5% to 10%, or 6% to 10%, or 7% to 10%, or 8% to 10%, or 9% to 10%. The porosity of the porous wall can be determined by mercury porosimetry according to ASTM standards D4284 and D6761, as described elsewhere herein (e.g., using an AutoPore V device (available from Micromeritics Instrument Corporation, USA)).

[0044] For the or each porous wall having a discontinuous porous structure, the porous regions may each have a median pore size of from about 10 to about 50 μm, e.g., from about 20 to about 40 μm, as determined by mercury porosimetry according to ASTM standards D4284 and D6761 as described elsewhere herein (e.g., using an AutoPore V device (available from Micromeritics Instrument Corporation, USA)).

[0045] The or each porous wall having a discontinuous porous structure may have a permeability of from about 10 to about 400 millidarcy, from about 10 to about 50 millidarcy, or from about 250 to about 400 millidarcy, or from about 100 to about 200 millidarcy, as determined by mercury porosimetry according to ASTM standards D4284 and D6761 using, for example, an AutoPore V device (available from Micromeritics Instrument Corporation, USA) as described elsewhere herein.

[0046] For the or each porous wall having a discontinuous porous structure, the porous regions may each have a characteristic length of from about 5 to about 60 μm, or from about 5 to about 20 μm, or from about 40 to about 60 μm, or from about 20 to about 50 μm, as determined by mercury porosimetry according to ASTM standards D4284 and D6761 as described elsewhere herein (e.g., using an AutoPore V device (available from Micromeritics Instrument Corporation, USA)).

[0047] The or each porous wall having a discontinuous porous structure may have a tortuosity of from about 10 to about 80, or from about 10 to about 30, or from about 30 to about 50, or from about 50 to 80, as determined by mercury porosimetry according to ASTM standards D4284 and D6761 as described elsewhere herein (e.g., using an AutoPore V device (available from Micromeritics Instrument Corporation, USA)).

[0048] For the or each porous wall having a discontinuous porous structure, each porous region has a diameter of 10,000 to 250,000 μm 2 wherein each cross-sectional area is determined as the volume of the porous region divided by the extent of the porous region along the thickness direction, and / or each porous region may have an average diameter of 25 to 250 μm.

[0049] Each porous region may have a generally circular (eg, circular) cross-section perpendicular to the path along which the porous region extends.

[0050] Each porous region may have an average diameter of 25 to 250 μm, e.g., 50 to 250 μm, 50 to 150 μm, 70 to 150 μm, or about 120 μm. The average diameter may be the average cross-sectional diameter along the length of each porous region.

[0051] Each porous region may have a midpoint diameter of 25-250 μm, e.g., 25-100 μm, 25-80 μm, or 25-50 μm. The midpoint diameter may be the diameter halfway along the length of the respective porous region.

[0052] Each porous region may have an entrance diameter of 25-250 μm, for example, 50-250 μm, 50-150 μm, 70-150 μm, or about 120 μm. The entrance diameter may be the diameter of the porous region on the entrance side of the respective wall.

[0053] Each porous region may have an exit diameter of 25-250 μm, for example, 50-250 μm, 50-150 μm, 70-150 μm, or about 120 μm. The exit diameter may be the diameter of the porous region at the exit side of the respective wall.

[0054] Each porous region is 10,000 to 250,000 μm 2 , for example, 15,000 to 250,000 μm 2 , 15,000~150,000μm 2 , 20,000~150,000μm 2 , 50,000~150,000μm 2 , or approximately 100,000 μm 2 The cross-sectional area of ​​the slit may be 0.05 mm.

[0055] Both the volume and extent of a porous region are determined by reference to a boundary of the porous region that does not extend beyond the region between the inlet and outlet sides of the body. Thus, even if a porous region is contiguous with an additional region of porous material (e.g., extending beyond the outlet side of the body), that additional region is not considered when assessing the volume and extent of the porous region, which is defined as a porous region extending through the body. Porous regions may each be defined as extending through the body between the inlet and outlet sides of the body or within a zone between the inlet and outlet sides of the body.

[0056] The body can be configured to prevent fluid flow therethrough except through porous regions. The body can be substantially non-porous, e.g., configured to have no flow paths therethrough except for discrete porous regions. The body can have a porosity of zero (open porosity).

[0057] One of the first and second outlet chambers can be an outer annular chamber and the other can be an inner central chamber surrounded by an inlet chamber having an annular configuration.

[0058] The first and second porous walls separating the respective first and second outlet chambers from the inlet chamber may be coaxial with each other.

[0059] The flow configuration may be configured such that each of the first and second outlet chambers is configured to only receive fluid flow through a respective porous wall.

[0060] The flow configuration may be configured such that the inlet chamber is only configured to accept fluid from outside the flow configuration through an inlet (e.g., the inlet is a single inlet or opening into the inlet chamber). Thus, all flow entering the outlet chamber passes through the porous region of the respective porous wall, and thus, the flow regime (e.g., flow rate) into the outlet chamber can be reliably controlled by controlling the properties of the porous region in the design of the flow configuration. Furthermore, when the porous walls provide electrodes for electrolysis, all flow entering the outlet chamber passes through the electrodes (e.g., through the electrocatalytic regions of the electrodes) rather than bypassing the active regions of the electrodes. The electrocatalytic regions may be referred to interchangeably as electrocatalytically active regions.

[0061] For the or each porous wall having a discontinuous porous structure, the material composition of the porous region may differ from the material composition of the body.

[0062] Each porous region may interface with the body at a respective boundary surrounding the porous region, and each such boundary may correspond to an interior wall of the body.

[0063] For the or each porous wall having a discontinuous porous structure, the body may be integrally formed with a plurality of porous regions, each porous region surrounding the porous region and interfacing with the body at a respective boundary defined by the change in porosity between the body and the porous region.

[0064] For the or each porous wall having a discontinuous porous structure, the body may be integrally formed with the respective plurality of porous regions by an additive manufacturing process.

[0065] For the or each porous wall having a discontinuous porous structure, the material composition of the body may be the same as the material composition of the respective porous region.

[0066] The inlet sides of the first and second porous walls may provide opposing surfaces that delimit the inlet chamber. As noted above, the porous walls correspond to electrodes of the electrolytic cell (e.g., they comprise or define electrodes when the flow configuration is implemented in the electrolytic cell).

[0067] There may be a substantially constant minimum separation distance to the opposing inlet side for at least 50% of the surface area of ​​one of the inlet sides, and the surfaces may be substantially locally parallel to each other.

[0068] It is desirable to both minimize the separation distance between opposing electrodes and to have the separation be substantially constant so as to provide a relatively uniform reaction rate along the extent of the electrodes. Even if the inlet side may not be electrocatalytically active in use (e.g., if provided with a passivation layer), any electrocatalytic region of the porous wall may terminate at the inlet side or may be at a substantially constant depth from the inlet side (e.g., within the porous region of the porous wall); therefore, such separation between opposing inlet sides of the porous wall is considered to represent a separation between the regions of the respective porous walls for ion exchange (e.g., the electrocatalytic regions of the respective porous walls).

[0069] The expression "locally parallel" is intended to mean that, when one or both of the porous walls are non-planar, a plane aligned with the local shortest separation vector from any point on one of the inlet sides to the other inlet side intersects the opposing inlet sides to define a substantially parallel line. For example, the opposing inlet sides may be cylindrical or conical and concentric, such that the inlet sides may not be globally parallel to each other about a common axis, and a plane that locally intersects the two boundaries along the local shortest separation vector will define two respective lines that are parallel to each other.

[0070] The first and second porous walls may each extend linearly parallel to the longitudinal direction (or axis) and may each be elongate along the longitudinal direction. Along the longitudinal extent of the porous walls that the porous walls are coextensive for ion exchange, the cross-section of the flow configuration may be substantially constant.

[0071] By configuring the flow configuration so that the porous walls have a constant cross-section that is coextensive for ion exchange, the configuration of the flow configuration can be easily adapted to increase or decrease the longitudinal length of the porous walls (and / or flow configuration, electrolyzer). For example, this may be appropriate to vary the capacity of the electrolyzer (e.g., as may be measured by reaction rate, flow rate for a given reaction efficiency (e.g., fraction of electrolyte solution reacted to produce each reaction product), or power input measured in kW).

[0072] The first and second porous walls may face each other along a longitudinal extent along which there is an average shortest separation distance between the inlet sides for ion exchange, and the ratio of the longitudinal extent to the average shortest separation distance may be 5 or more, for example 10 or more.

[0073] This ratio corresponds to the elongated configuration of the flow configuration, particularly the elongated configuration of the separation gap between opposing porous walls. While it is generally known that it is desirable to reduce the separation distance between opposing electrodes, the longitudinal extent of the porous walls along which this is possible in the configurations discussed above may be limited by the means for keeping the reaction products produced at each electrode separated (e.g., ion exchange membranes or laminar flow buffers, i.e., by flow between the electrodes maintaining laminar flow conditions to prevent reaction products from migrating from one side to the other). In the configurations discussed above, those means for keeping the reaction products separated tend to involve ion exchange membranes or be difficult to maintain over any significant longitudinal extent. The present invention allows the porous walls (and therefore the electrodes) to be separated by an elongated separation gap, i.e., a separation gap having a length / extent (along which the electrolyte flows) that is much greater than the separation distance between the porous walls. Without wishing to be bound by theory, it is believed that this may be made possible by the use of porous walls that provide resistance to reverse flow from the outlet chamber to the inlet chamber, preventing reverse flow without relying on high flow inertia from the inlet chamber to the outlet chamber. High flow inertia may be achieved by providing a relatively small flow volume, which tends to reduce the surface area of ​​the porous wall. By using porous walls that suppress reverse flow rather than relying on high flow inertia, the flow volume for a given mass flow through the porous wall can be increased. This allows the separation gap between the porous walls to be essentially elongated, thereby increasing the ratio between the surface area of ​​the porous wall for the electrolytic reaction and the volume of fluid within the separation gap. The velocity of the electrolyte (e.g., as can be measured by referring to the fraction of the volume of electrolyte solution reacted as it passes through the electrolytic cell) tends to increase as these ratios (i.e., the ratio between the surface area of ​​each of the electrodes and the volume of electrolyte solution within the separation gap between those electrodes) increase.

[0074] The flow arrangement according to the first aspect may comprise or be defined by the electrolytic cells of the electrolytic cell.

[0075] According to a second aspect, an electrolytic cell for carrying out continuous electrolysis of an electrolyte liquid is disclosed, comprising a flow arrangement according to the first aspect or the seventh aspect (described below) for receiving the electrolyte liquid at an inlet, wherein a first porous wall and a second porous wall provide a first electrode and a second electrode of the electrolytic cell, respectively.

[0076] The electrolytic cell may include a controller, the controller configured to maintain supercritical conditions of the electrolyte liquid in the first porous wall and / or the second porous wall.

[0077] The controller can be configured to maintain supercritical conditions of the electrolyte liquid in the first porous wall and / or the second porous wall by controlling the flow control device to maintain a target inlet pressure and a target inlet temperature of the electrolyte liquid at the inlet, and / or by controlling the current through the first electrode and the second electrode and / or the voltage applied between the first electrode and the second electrode.

[0078] For example, heating of the electrolyte liquid to a critical temperature corresponding to the supercritical condition of the electrolyte liquid can be provided in the or each respective porous wall (electrode) of the electrolytic cell.

[0079] The controller can be configured to control a flow control device, e.g., a heater, such that the electrolyte solution is provided to the inlet at a temperature within 50°C (e.g., within 30°C or within 20°C) of a critical temperature, e.g., the critical temperature of the aqueous electrolyte solution of 374°C.

[0080] The controller can be configured to control flow control devices, such as, for example, a compressor and / or one or more discharge valves associated with the electrolytic cell, to maintain a target inlet pressure. The target inlet pressure may be at least the critical pressure of the respective electrolyte solution. For example, the target inlet pressure may be at least 22 MPa for an aqueous electrolyte solution.

[0081] A controller can be configured to control the flow control device to maintain supercritical conditions of the electrolyte liquid in the inlet chamber and in the first and second outlet chambers.

[0082] The controller can be configured to control the flow control device such that the electrolyte liquid is provided to the inlet at supercritical conditions.

[0083] The flow control device may comprise a heater configured to heat the electrolyte liquid upstream of the inlet chamber. The heater may be part of the electrolytic cell or may be located with the electrolytic cell in (or within) the electrolysis facility.

[0084] The flow control device may comprise a compressor configured to compress the electrolyte liquid upstream of the inlet chamber. The flow control device may be part of the electrolytic cell or may be located with the electrolytic cell in (or within) the electrolysis facility.

[0085] The supercritical conditions for the electrolyte liquid may be supercritical pressure and temperature conditions of a pressure of at least 22 MPa and a temperature of at least 374° C. for an aqueous electrolyte liquid.

[0086] The supercritical conditions may be a pressure of 22-27 MPa and a temperature of 374°C-550°C, e.g., 374°C-400°C. By maintaining supercritical conditions in the first and second porous walls, losses associated with the electrolysis reaction can be reduced by (i) suppressing the formation of reaction product bubbles on the surfaces of the electrodes and / or by increasing the conductivity of the electrolyte solution for a given electrolyte concentration for a given amount of electrolyte (or conversely, achieving adequate conductivity using a relatively lower concentration of electrolyte).

[0087] Although some examples discussed herein relate to operation at supercritical conditions, and the appended claims refer to electrolytic cells or electrolytic cell installations in which a controller is configured to maintain supercritical conditions, the present disclosure contemplates electrolytic cells and electrolytic cell installations and methods of operation in which no such controller or control is present for maintaining supercritical conditions of the electrolyte solution, as described herein (e.g., by any combination of features contemplated in this disclosure).

[0088] The electrolytic cell can include a controller configured to control the flow control device to provide the electrolyte liquid to the inlet chamber at an inlet temperature of at least 320°C, e.g., at least 350°C. The inlet temperature can be below the critical temperature of the respective electrolyte liquid, e.g., 374°C for aqueous electrolyte liquids. The inlet temperature can be within 50°C (e.g., within 30°C or within 20°C) of the critical temperature of the electrolyte liquid. The inlet temperature can be between 320°C and less than 374°C, e.g., between 350°C and 370°C or between 350°C and 360°C. The controller can be configured to control the flow control device to provide the electrolyte liquid to the inlet chamber at a pressure below or greater than the critical pressure of the respective electrolyte liquid (e.g., 22 MPa for aqueous electrolyte liquids). The controller can be configured to control the flow device to provide the electrolyte liquid to the inlet chamber at a pressure of at least 22 MPa.

[0089] The inlet temperature and inlet pressure may be controlled (eg, by controlling flow control devices) to maintain subcritical conditions throughout the inlet and outlet chambers.

[0090] The flow control device may comprise a first release valve and a second release valve as defined below. Such valves may be part of the electrolytic cell or may be installed with the electrolytic cell in (or within) the electrolysis facility. The first release valve and / or the second release valve may be variable control valves.

[0091] The electrolytic cell may have a first outlet associated with the first outlet chamber for discharging a fluid reaction product produced at the first electrode and a second outlet associated with the second outlet chamber for discharging a fluid reaction product produced at the second electrode. The flow control device may include a first discharge valve and a second discharge valve in fluid communication with the first outlet and the second outlet, respectively.

[0092] The first release valve may be configured to maintain a first target pressure upstream of the valve, and the second release valve may be configured to maintain a second target pressure upstream of the valve.

[0093] The first and second release valves may be configured to maintain different target pressures to create pressure drops across each of the respective porous walls to control respective branch flows of electrolyte liquid driven from the inlet chamber through the respective porous walls and into the respective outlet chambers, and the controller may be configured to control the first and / or second release valves to maintain the respective target pressures.

[0094] The controller may be configured to control the first and / or second discharge valves to maintain a target flow rate or composition from one or each of the first and second outlets based on flow rate data, upstream pressure data, and / or composition data received by the controller, and / or to maintain a target flow rate ratio between the flows out of the first and second outlets based on flow rate data, upstream pressure data, and / or composition data received by the controller. The target flow rate ratio may correspond to the ratio of the total flow rate out of the first outlet to the total flow rate out of the second outlet, or the ratio of the flow rate of the first fluid reaction product out of the first outlet to the flow rate of the second fluid reaction product out of the second outlet.

[0095] The controller may be configured to control the first and / or second discharge valves to maintain respective target flow rates or respective target compositions of the streams from each of the first and second outlets based on flow rate data and / or composition data received by the controller for the respective discharge streams.

[0096] The target flow rate as referred to above may be the total flow rate from each outlet, or it may be the flow rate of a particular component fluid of the mixture flowing from each outlet, for example, the flow rate of oxygen in a mixture containing oxygen and electrolyte liquid, or the flow rate of hydrogen in a mixture containing oxygen and electrolyte liquid. The target flow rate may be a mass flow rate.

[0097] The flow rate data may be determined by sensors in the electrolytic cells or in the equipment in which the electrolytic cells are installed. For example, a flow meter may be present downstream of each respective discharge valve. One or more flow meters may be present downstream of a separate device in the equipment in which the electrolytic cells are installed. For example, a separation device may separate the streams discharged through each outlet into a respective reaction product stream and an electrolyte (or water) stream, and a flow meter may be installed on the separation means or at each outlet to monitor the flow rate of each component (i.e., reaction product and electrolyte). The combination of the discharge valves, the flow meters for monitoring the flow rates through the respective valves, and a controller that controls the discharge valves based on signals from the flow meters can provide a mass flow controller, which controls the discharge valves based on signals from the flow meters to maintain a target flow rate.

[0098] The upstream pressure data may be determined by one or more pressure sensors in the electrolytic cell or in the facility in which the electrolytic cell is installed to monitor the pressure of the electrolyte solution upstream of the valve. For example, a pressure sensor may extend into one or each of the outlet chambers holding the respective reaction products and be configured to send a respective pressure signal to the controller, or a differential pressure sensor (which may be a differential pressure transducer) may be configured to respond to a pressure difference between the chambers and send a differential pressure signal to the controller. For example, the controller may be calibrated to maintain the or each respective pressure within a respective target range or differential pressure within a target range to maintain target operating conditions (e.g., a target flow rate of one or each respective reaction product through the outlet, as an example).

[0099] The target composition may be a target proportion of the fluid reaction product in the stream discharged through each outlet. The composition may be a mass fraction. The composition data may be obtained based on monitoring the flow rate of each component (i.e., each reaction product and electrolyte liquid) of the stream discharged through each outlet.

[0100] The controller may not receive flow rate or composition data from which a numerical value of the flow rate or component mass fraction can be derived, but may receive data related to the flow rate or composition of the stream that can be used to control the or each release valve so that a target flow rate, composition, or flow rate ratio can be maintained by appropriately calibrating the controller.

[0101] The controller may be configured to determine whether an excessive amount of the second fluid reaction product is present in the outlet stream through the first outlet and / or whether an excessive amount of the first fluid reaction product is present in the outlet stream through the second outlet based on composition data received at the controller for each outlet stream. The controller may be configured to control the first and / or second release valves to vary the flow rate through the porous wall of the electrolytic cell based on said determination.

[0102] For example, the controller may control the first and / or second release valves to increase the pressure drop from the inlet chamber to the respective outlets to increase the flow rate through the respective outlets. For example, when an outlet is downstream of a porous wall, increasing the flow rate through the porous wall may inhibit backflow of reaction products through the porous wall (e.g., due to inertia of the flow through the porous wall).

[0103] The controller may be configured to maintain thermodynamic and / or flow rate conditions of the electrolyte liquid through the electrolytic cell (e.g., by controlling the flow rate through the electrolytic cell to match the determined thermodynamic conditions of the electrolyte liquid) corresponding to a Reynolds number in the inlet chamber of not more than 4000, e.g., not more than 2300. Controlling the conditions of the electrolyte liquid to meet the above Reynolds number criteria can prevent turbulence and / or transient mixing in the inlet chamber that could otherwise promote migration of reaction products between the electrodes across the separating gap between the electrodes.

[0104] For the or each porous wall having a discontinuous porous structure and providing an electrode of the electrolytic cell, the porous regions may contain an electrocatalyst, thereby defining an electrocatalytic region of the respective electrode for the electrolytic half-reaction.

[0105] The term "electrocatalyst" as used herein refers to an electrocatalyst (e.g., an electrocatalytically active material) suitable for catalyzing a half-reaction of the electrolysis of an electrolyte solution. The provision of such an electrocatalyst is considered to provide an associated electrocatalytic area of ​​the porous wall that is electrocatalytically active (i.e., for each half-reaction of the electrolysis). The electrolysis reaction may be the electrolysis of water or an aqueous (aqueous) electrolyte solution. Thus, the electrocatalyst may be an electrocatalyst suitable for catalyzing a half-reaction of the electrolysis of water.

[0106] Electrocatalysts include precious metals (i.e., Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Re), d-block transition metals (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, R, Os, Ir, Pt, Au, Hg, Rf, Db, S, Rh, Hs, Mt, Ds, Rg, Cn), f-block lanthanides (i.e., La, Ce, Pr, Nd, Pm, Sm, Eu, Gd) , Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (i.e., Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), platinum group metals (i.e., Ru, Rh, Pd, Os, Ir, Pt), P, S, C, and / or combinations thereof. The one or more elements may be present in elemental form (e.g., as a (substantially) pure metal), in a mixture (e.g., an alloy), in a compound (e.g., an oxide, hydroxide, nitride, boride, sulfide, phosphide, carbonate, and / or organic compound such as a metal-organic framework), and / or incorporated into a nanomaterial such as a nanoparticle, nanotube (e.g., carbon nanotube), nanocage (e.g., fullerene), and / or nanosheet (e.g., graphene).

[0107] The electrocatalyst may include (e.g., consist essentially of, consist of, or be) Co, Fe, Ir, Li, Ni, P, S, Ti, Zn, and / or combinations thereof.

[0108] The electrocatalyst may include (e.g., consist essentially of, consist of, or be) Ce, Co, Fe, Ho, Ir, Mo, Ni, Pd, Pt, Ru, Sm, W, and / or combinations thereof.

[0109] The electrocatalyst may include (e.g., consist essentially of, consist of, or be) Ni, Fe, Co, P, S, and / or combinations thereof.

[0110] The electrocatalyst may include (eg, consist essentially of, consist of, or be) Pt, Ir, Pd, Ni, Mo, and / or combinations thereof.

[0111] In some examples, the electrocatalyst includes (eg, consists essentially of, consists of, or is) Ni (eg, elemental Ni) or Pt (eg, elemental Pt).

[0112] In some examples, the electrocatalyst includes (eg, consists essentially of, consists of, or is) Ni (eg, elemental Ni).

[0113] In some examples, the electrocatalyst includes (eg, consists essentially of, consists of, or is) Pt (eg, elemental Pt).

[0114] The electrocatalyst may be provided in the form of, or formed from, electrocatalyst-containing particulates. Particles of the electrocatalyst-containing particulates may comprise (e.g., consist essentially of, or consist of) the electrocatalyst. The electrocatalyst-containing particulates may comprise (e.g., consist essentially of, or consist of) particles of the electrocatalyst.

[0115] For example, electrocatalyst-containing microparticles may be prepared from noble metals (i.e., Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Re), d-block transition metals (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, R, Os, Ir, Pt, Au, Hg, Rf, Db, S, Rh, Hs, Mt, Ds, Rg, Cn), f-block lanthanides (i.e., La, Ce, Pr, Nd, The SiO 2 layer may comprise (e.g., consist essentially of, or consist of) one or more elements selected from rare earth metals (i.e., Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (i.e., Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), platinum group metals (i.e., Ru, Rh, Pd, Os, Ir, Pt), P, S, C, and / or combinations thereof. The one or more elements may be present in elemental form (e.g., as a (substantially) pure metal), in a mixture (e.g., an alloy), in a compound (e.g., an oxide, hydroxide, nitride, boride, sulfide, phosphide, carbonate, and / or organic compound such as a metal-organic framework), and / or incorporated into a nanomaterial such as a nanoparticle, nanotube (e.g., carbon nanotube), nanocage (e.g., fullerene), and / or nanosheet (e.g., graphene).

[0116] The electrocatalyst-containing particulates may include (e.g., may consist essentially of, or may consist of) particles comprising (e.g., may consist essentially of, or may consist of) Co, Fe, Ir, Li, Ni, P, S, Ti, Zn, and / or combinations thereof.

[0117] The electrocatalyst-containing particulates may include (e.g., may consist essentially of, or may consist of) particles comprising (e.g., may consist essentially of, or may consist of) Ce, Co, Fe, Ho, Ir, Mo, Ni, Pd, Pt, Ru, Sm, W, and / or combinations thereof.

[0118] The electrocatalyst-containing particulates may include (e.g., may consist essentially of, or may consist of) particles comprising (e.g., consisting essentially of, or consisting of) Ni, Fe, Co, P, S, and / or combinations thereof.

[0119] The electrocatalyst-containing particulates may include (e.g., may consist essentially of, or may consist of) particles comprising (e.g., consisting essentially of, or consisting of) Pt, Ir, Pd, Ni, Mo, and / or combinations thereof.

[0120] In some examples, the electrocatalyst-containing particulates include (e.g., consist essentially of, or consist of) particles comprising (e.g., consist essentially of, or consist of) Ni (e.g., elemental Ni) or Pt (e.g., elemental Pt).

[0121] In some examples, the electrocatalyst-containing particulates include (e.g., consist essentially of, or consist of) particles that include (e.g., consist essentially of, or consist of) Ni (e.g., elemental Ni).

[0122] In some examples, the electrocatalyst-containing particulates include (e.g., consist essentially of, or consist of) particles that include (e.g., consist essentially of, or consist of) Pt (e.g., elemental Pt).

[0123] In some examples, the electrocatalyst-containing particulate is a Ni-containing particulate. The Ni-containing particulate may include (e.g., consist essentially of, or consist of) particles of Ni (e.g., elemental Ni) or a Ni-based alloy.

[0124] In some examples, the electrocatalyst-containing particulate is a Ni particulate consisting essentially of Ni particles.

[0125] For the or each porous wall having a discontinuous porous structure and providing an electrode for an electrolytic cell, each respective porous region may contain an electrocatalyst formed from electrocatalyst-containing particulates.

[0126] The porous media may be formed by agglomerating electrocatalyst-containing particulates. In other words, each of the porous regions may contain an electrocatalyst provided in the form of an agglomerated porous media.

[0127] As used herein, the term "agglomeration" refers to the process of physically and / or chemically adhering particles of the electrocatalyst-containing particulate to one another to form a porous medium. Agglomeration of the electrocatalyst-containing particulate may include sintering the electrocatalyst-containing particulate, fusing the electrocatalyst-containing particulate, and / or bonding the particles of the electrocatalyst-containing particulate to one another with a binder and / or a chemical reaction.

[0128] For example, the porous medium may be formed by sintering electrocatalyst-containing particulates. It will be appreciated that sintering is a process of forming a solid mass of material from particulates by applying heat and / or pressure without melting the particulates to their liquidus point. During sintering, particles of the particulates may bond together by atomic and / or molecular diffusion between adjacent particles at temperatures below the melting point of the material. Plastic deformation of the particles may also occur.

[0129] Thus, each respective porous region may include an electrocatalyst provided in the form of a sintered porous media.

[0130] Porous media may be formed by melting electrocatalyst-containing particulates. It will be appreciated that melting is a process involving the dissolution of a solid material into a liquid. Porous media may be formed from particulates by heating the particulates to a temperature at which localized melting (e.g., melting at the particle surface) occurs, resulting in bonding of adjacent particles while avoiding overall liquefaction of the particulates.

[0131] Thus, each respective porous region may include an electrocatalyst provided in the form of a molten porous media.

[0132] The porous medium may be formed by binding particles of the electrocatalyst-containing particulate together using a binder. The binder may be a polymeric binder, such as a thermoplastic binder or a thermosetting binder (e.g., resin). A thermoplastic binder is a polymeric binder that melts or becomes flexible at elevated temperatures and solidifies upon cooling. A thermosetting binder (e.g., resin) is a polymeric binder that irreversibly hardens (i.e., cures) upon heating, exposure to radiation, and / or exposure to an appropriate catalyst.

[0133] The porous medium may be formed by bonding particles of the electrocatalyst-containing particulate together through a chemical reaction. For example, a chemical reaction may occur that forms a reaction product that bonds adjacent particles together. The chemical reaction may be an oxidation reaction, e.g., the growth of an oxide layer on the surface of the particles, which bonds adjacent particles together. The chemical reaction may occur, for example, at elevated temperatures upon exposure to a suitable (e.g., oxidizing) atmosphere.

[0134] Thus, each respective porous region may include an electrocatalyst provided in the form of a bound porous media.

[0135] The (e.g., aggregated, sintered, fused, and / or bonded) porous media can be filled with precious metals (i.e., Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Re), d-block transition metals (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, R, Os, Ir, Pt, Au, Hg, Rf, Db, S, Rh, Hs, Mt, Ds, Rg, Cn), f-block lanthanides (i.e., La, The SiO 2 layer may comprise (e.g., consist essentially of, or consist of) one or more elements selected from: rare earth metals (i.e., Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (i.e., Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), platinum group metals (i.e., Ru, Rh, Pd, Os, Ir, Pt), P, S, C, and / or combinations thereof. The one or more elements may be present in elemental form (e.g., as a (substantially) pure metal), in a mixture (e.g., an alloy), in a compound (e.g., an oxide, hydroxide, nitride, boride, sulfide, phosphide, carbonate, and / or organic compound such as a metal-organic framework), and / or incorporated into a nanomaterial such as a nanoparticle, nanotube (e.g., carbon nanotube), nanocage (e.g., fullerene), and / or nanosheet (e.g., graphene).

[0136] The (e.g., aggregated, sintered, fused, and / or bonded) porous medium may include (e.g., may consist essentially of, or may consist of) particles comprising (e.g., may consist essentially of, or may consist of) Co, Fe, Ir, Li, Ni, P, S, Ti, Zn, and / or combinations thereof.

[0137] The (e.g., aggregated, sintered, fused, and / or bonded) porous medium may include (e.g., may consist essentially of, or may consist of) particles comprising (e.g., may consist essentially of, or may consist of) Ce, Co, Fe, Ho, Ir, Mo, Ni, Pd, Pt, Ru, Sm, W, and / or combinations thereof.

[0138] The (e.g., aggregated, sintered, fused, and / or bonded) porous media may include (e.g., consist essentially of, or consist of) Ni, Fe, Co, P, S, and / or combinations thereof.

[0139] The (e.g., aggregated, sintered, fused, and / or bonded) porous medium may include (e.g., consist essentially of, or consist of) Pt, Ir, Pd, Ni, Mo, and / or combinations thereof.

[0140] The (e.g., aggregated, sintered, fused, and / or bonded) porous medium may include (e.g., consist essentially of, or consist of) Ni (e.g., elemental Ni) or Pt (e.g., elemental Pt).

[0141] The (eg, aggregated, sintered, fused, and / or bonded) porous medium may include (eg, consist essentially of, or consist of) Ni (eg, elemental Ni).

[0142] The (eg, aggregated, sintered, fused, and / or bonded) porous medium may include (eg, consist essentially of, or consist of) Pt (eg, elemental Pt).

[0143] The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% or more by weight, e.g., about 60% or more by weight, or about 70% or more by weight, or about 80% or more by weight, or about 90% or more by weight, or about 95% or more by weight, or 99% or more by weight of electrocatalyst. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 100% or less by weight, e.g., about 99% or less by weight, or about 95% or less by weight, or about 90% or less by weight of electrocatalyst. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% to about 100% by weight of the electrocatalyst, e.g., about 60% to about 100% by weight, or about 70% to about 100% by weight, or about 80% to about 100% by weight, or about 90% to about 100% by weight, or about 95% to about 100% by weight, or about 99% to about 100% by weight.

[0144] The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50 wt. %, e.g., 60 wt. % or more, or about 70 wt. % or more, or about 80 wt. % or more, or about 90 wt. % or more, or about 95 wt. % or more, or about 99 wt. % or more of a noble metal (i.e., Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Re), a d-block transition metal (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, T The metals may include a, W, R, Os, Ir, Pt, Au, Hg, Rf, Db, S, Rh, Hs, Mt, Ds, Rg, Cn), f-block lanthanides (i.e., La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (i.e., Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), platinum group metals (i.e., Ru, Rh, Pd, Os, Ir, Pt), P, S, C and / or combinations thereof. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may be about 100 wt. % or less, e.g., about 99 wt. % or less, or about 95 wt. % or less, or about 90 wt. % or less of precious metals (i.e., Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Re), d-block transition metals (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, R, Os, Ir, Pt, Au, Ag, Re), The metals may include ruthenium, argon, argon, argon-containing metals (e.g., ruthenium, argon, argon-containing metals ...The (e.g., aggregated, sintered, fused, and / or bonded) porous media can be about 50% to about 100% by weight, e.g., about 60% to about 100% by weight, or about 70% to about 100% by weight, or about 80% to about 100% by weight, or about 90% to about 100% by weight, or about 95% to about 100% by weight, or about 99% to about 100% by weight of a precious metal (i.e., Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Re), a d-block transition metal (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, The metals may include Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, R, Os, Ir, Pt, Au, Hg, Rf, Db, S, Rh, Hs, Mt, Ds, Rg, Cn), f-block lanthanides (i.e., La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (i.e., Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), platinum group metals (i.e., Ru, Rh, Pd, Os, Ir, Pt), P, S, C and / or combinations thereof.

[0145] The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% by weight or more, e.g., about 60% by weight or more, or about 70% by weight or more, or about 80% by weight or more, or about 90% by weight or more, or about 95% by weight or more, or 99% by weight or more Co, Fe, Ir, Li, Ni, P, S, Ti, Zn, and / or combinations thereof. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 100% by weight or less, e.g., about 99% by weight or less, or about 95% by weight or less, or about 90% by weight or less Co, Fe, Ir, Li, Ni, P, S, Ti, Zn, and / or combinations thereof. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% to about 100% by weight, e.g., about 60% to about 100% by weight, or about 70% to about 100% by weight, or about 80% to about 100% by weight, or about 90% to about 100% by weight, or about 95% to about 100% by weight, or about 99% to about 100% by weight of Co, Fe, Ir, Li, Ni, P, S, Ti, Zn, and / or combinations thereof.

[0146] The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% by weight or more, e.g., about 60% by weight or more, or about 70% by weight or more, or about 80% by weight or more, or about 90% by weight or more, or about 95% by weight or more, or 99% by weight or more of Ce, Co, Fe, Ho, Ir, Mo, Ni, Pd, Pt, Ru, Sm, W, and / or combinations thereof. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 100% by weight or less, e.g., about 99% by weight or less, or about 95% by weight or less, or about 90% by weight or less of Ce, Co, Fe, Ho, Ir, Mo, Ni, Pd, Pt, Ru, Sm, W, and / or combinations thereof. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% to about 100% by weight, e.g., about 60% to about 100% by weight, or about 70% to about 100% by weight, or about 80% to about 100% by weight, or about 90% to about 100% by weight, or about 95% to about 100% by weight, or about 99% to about 100% by weight of Ce, Co, Fe, Ho, Ir, Mo, Ni, Pd, Pt, Ru, Sm, W, and / or combinations thereof.

[0147] The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% by weight or more, e.g., about 60% by weight or more, or about 70% by weight or more, or about 80% by weight or more, or about 90% by weight or more, or about 95% by weight or more, or 99% by weight or more of Ni, Fe, Co, P, S, and / or combinations thereof. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 100% by weight or less, e.g., about 99% by weight or less, or about 95% by weight or less, or about 90% by weight or less of Ni, Fe, Co, P, S, and / or combinations thereof. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise from about 50% to about 100% by weight, e.g., from about 60% to about 100% by weight, or from about 70% to about 100% by weight, or from about 80% to about 100% by weight, or from about 90% to about 100% by weight, or from about 95% to about 100% by weight, or from about 99% to about 100% by weight of Ni, Fe, Co, P, S, and / or combinations thereof.

[0148] The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% by weight or more, e.g., about 60% by weight or more, or about 70% by weight or more, or about 80% by weight or more, or about 90% by weight or more, or about 95% by weight or more, or 99% by weight or more Pt, Ir, Pd, Ni, Mo, and / or combinations thereof. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 100% by weight or less, e.g., about 99% by weight or less, or about 95% by weight or less, or about 90% by weight or less Pt, Ir, Pd, Ni, Mo, and / or combinations thereof. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% to about 100% by weight, e.g., about 60% to about 100% by weight, or about 70% to about 100% by weight, or about 80% to about 100% by weight, or about 90% to about 100% by weight, or about 95% to about 100% by weight, or about 99% to about 100% by weight of Pt, Ir, Pd, Ni, Mo, and / or combinations thereof.

[0149] The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50 wt% or more, e.g., about 60 wt% or more, or about 70 wt% or more, or about 80 wt% or more, or about 90 wt% or more, or about 95 wt% or more, or 99 wt% or more Ni and / or Pt. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 100 wt% or less Ni and / or Pt, e.g., about 99 wt% or less, or about 95 wt% or less, or about 90 wt% or less Ni and / or Pt. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% to about 100% by weight Ni and / or Pt, e.g., about 60% to about 100% by weight, or about 70% to about 100% by weight, or about 80% to about 100% by weight, or about 90% to about 100% by weight, or about 95% to about 100% by weight, or about 99% to about 100% by weight.

[0150] The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50 wt% or more, e.g., about 60 wt% or more, or about 70 wt% or more, or about 80 wt% or more, or about 90 wt% or more, or about 95 wt% or more, or 99 wt% or more Ni. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 100 wt% or less, e.g., about 99 wt% or less, or about 95 wt% or less, or about 90 wt% or less Ni. The (e.g., aggregated, sintered, fused, and / or bonded) porous media may comprise about 50% to about 100% by weight Ni, e.g., about 60% to about 100% by weight, or about 70% to about 100% by weight, or about 80% to about 100% by weight, or about 90% to about 100% by weight, or about 95% to about 100% by weight, or about 99% to about 100% by weight.

[0151] For the or each porous wall having a discontinuous porous structure, the material composition of the porous region may differ from the material composition of the body, and the body may comprise a passive region of each electrode for suppressing electrolysis.

[0152] For the or each porous wall having a discontinuous porous structure, the body may be integrally formed with a plurality of porous regions, each porous region surrounding the porous region and interfacing with the body at a respective boundary defined by the change in porosity between the body and the porous region, the porous regions containing the electrocatalyst and thus belonging to the electrocatalytic region of the respective electrode for the electrolytic half-reaction, and the porous regions and the body may have a common material composition containing the electrocatalyst.

[0153] The material composition of the body that is common to the material composition of each porous region may be the material composition of a core portion of the body that surrounds and is adjacent to each of the porous regions. The material composition of the body that is common to the material composition of each porous region may be the non-coating material composition of the body (i.e., the material coating of the body excluding any coating). For example, the body may include a coating (e.g., a passivation coating) that defines an inlet side of the body, the passivation coating having a different composition than the core portion of the body.

[0154] For the or each porous wall having a discontinuous structure, the porous wall may additionally be configured for an electrolytic reaction on the outlet side of the porous wall, for example, the outlet side of the porous wall may include an electrocatalyst and be configured to react with the electrolyte liquid.

[0155] The porous walls may be formed by an additive manufacturing process to provide an integrally formed body and porous region.

[0156] For the or each porous wall having a discontinuous porous structure, the inlet side of the body may be defined by a passive region configured to be less electrocatalytically active than the electrocatalytic region, and the passive region may include a passivation coating defining the inlet side of the body for suppressing electrolysis.

[0157] A passive region as defined with respect to any of the above statements may be configured to inhibit a respective half-reaction of the electrolysis. By providing a passive region (e.g., by the body as a whole, by a core or uncoated portion of the body, or at the inlet side of the body, e.g., as provided by a passivating coating), a respective half-reaction of the electrolysis may be inhibited or prevented from occurring at the inlet side of the porous walls, such that the reaction may occur only or primarily upon electrolyte solution (and / or respective ions) entering one of the porous regions (and / or passing through the porous region to reach the electrocatalytic region defining the outlet side of the porous walls).

[0158] The passive regions (and any passive regions as described herein) may be configured to suppress electrolysis by being less electrocatalytically active (for each half-reaction of the electrolysis of the electrolyte solution) than the electrocatalytic regions. The rate of each half-reaction within the passive regions (as a whole) may be lower than the rate of each half-reaction within the electrocatalytic regions (as a whole), thereby making the passive regions less electrocatalytically active than the electrocatalytic regions. The rate of each half-reaction may be the production rate of the respective fluid reaction product (e.g., hydrogen or oxygen, depending on the electrode) within the respective region, e.g., the mass of fluid reaction product produced per unit time (e.g., g / s of hydrogen), or the current density (e.g., in A) integrated across the electrolyte interface of the respective region, where the electrolyte interface is the surface of the respective region configured to contact the electrolyte solution. As used herein, the rate of each region is the aggregate rate of the respective region, rather than a specific rate per unit volume, thickness, mass, or surface area (e.g., of the porous wall or of the electrolyte interface of each region of the porous wall), etc. The passive region and the electrocatalytic region may be configured such that the rate of each half-reaction in the passive region (as a whole) can be lower than the rate of each half-reaction in the electrocatalytic region (as a whole). For example, the rate in the passive region may be no more than 50%, no more than 20%, no more than 10%, no more than 5%, or no more than 1% of the rate in the electrocatalytic region. The rate in the passive region may be substantially zero.

[0159] The passive region may contain less electrocatalyst (for electrocatalyzing each half-reaction of the electrolysis of the electrolyte solution) than the electrocatalytic region, e.g., less of the same electrocatalyst as the electrocatalytic region, and / or any electrocatalyst in the passive region may be less electrocatalytically active for each half-reaction than the electrocatalyst in the electrocatalytic region.

[0160] A passive region may include less electrocatalyst at the passive region's electrolyte interface with the electrolyte liquid (i.e., within the surface area of ​​the passive region that contacts the electrolyte liquid during use) than is present at the electrolyte interface of the electrocatalyst region (i.e., within the surface area of ​​the electrocatalyst region). In other words, the material composition of the passive region at the electrolyte interface of the passive region (i.e., within the surface area) may include less electrocatalyst than the material composition of the electrocatalyst region at the respective electrolyte interface. For example, this may include less than 5 wt. % electrocatalyst, less than 1 wt. % electrocatalyst, or less than 0.1 wt. % electrocatalyst. The composition of a passive region at an electrolyte interface may be evaluated by reference to a surface area of ​​the passive region adjacent to the electrolyte liquid during use, e.g., having a thickness of 1 μm.

[0161] The electrocatalytic region referred to herein may have a first composition. The passive region referred to herein may have a second composition. The nominal electrode for carrying out each half-reaction of the electrolysis of the electrolyte solution in the nominal cell may have a surface region adjacent to the electrolyte solution at the electrolyte interface of the nominal electrode. The surface region may have a thickness of 1 μm from the electrolyte interface.

[0162] The first composition and the second composition are such that a nominal electrode in a nominal cell has a surface area of ​​10 mA cm 2 when the surface area of ​​the nominal electrode has the first composition. -2 For example, at a nominal pressure and temperature of 22.5 MPa and 375°C, the overvoltage required to reach a current density of 10 mA cm at a nominal electrode in a nominal cell when the surface area of ​​the nominal electrode has the second composition. -2 The overpotential may be selected to be at least half, at least a third, or at least a fifth of the overpotential required to reach a current density of 1000 kJ / s.

[0163] Each half-reaction can be suppressed by providing a passive region as a passivation layer or coating as discussed elsewhere herein.

[0164] The statements above relating to the electrocatalytic regions, passive regions, and their characterization as electrocatalytically active or less electrocatalytically active regions are provided above and below and may apply to any of the embodiments and statements as discussed below in the detailed description.

[0165] When the passive region includes a passivating coating defining the inlet side of the porous wall, the passivating coating may be a dielectric coating, such as, for example, an oxide coating (e.g., an inorganic metal oxide coating), such as silica (SiO), zinc oxide (ZnO), or zirconia (ZrO). All references herein to passivation or providing a passivating coating may include applying a dielectric coating, such as a coating of the exemplary materials described in the preceding sentence. The passivating coating may be provided by CVD (chemical vapor deposition) of a passivating material, such as, for example, alumina (AlO), zirconia (ZrO), or titania (TiO).

[0166] By passivating the inlet side of the porous wall, each fluid reaction product produced at the electrode may be produced only at a location downstream from the inlet chamber (e.g., within the porous region of the porous wall or on the outlet side of the porous wall), rather than on the inlet side that bounds the inlet chamber, thereby inhibiting each fluid reaction product from being produced in or migrating to the inlet chamber.

[0167] Regardless of the provision of a passive region, any fluid reaction product produced in or provided to the outlet chamber (e.g., by reaction with an electrocatalytic region at or defining the outlet side of the composite porous electrode) may be inhibited from flowing back through the porous wall because the less dense fluid reaction product must flow downward through the porous region against buoyancy forces (this flow may also oppose a pressure gradient across the porous wall). This may be referred to as inhibiting return flow due to a downstream-biased buoyancy effect, because the buoyancy forces within the porous region promote downstream flow to the outlet chamber rather than upstream flow to the inlet chamber.

[0168] According to a third aspect, a source of electrolyte solution (e.g., an aqueous electrolyte solution); an electrolytic cell according to the second aspect for carrying out continuous electrolysis of an electrolyte solution; An electrolysis facility is disclosed comprising:

[0169] The electrolysis facility may comprise a plurality of electrolytic cells according to the first aspect of the present invention. The electrolysis facility may comprise a flow control device as defined herein.

[0170] According to a fourth aspect, there is provided a method of operating an electrolytic cell according to the second aspect or an electrolytic cell according to the third aspect, comprising the steps of: providing an inlet flow of electrolyte liquid to the inlet chamber via the inlet for carrying out electrolytic half-reactions at first and second electrodes provided by the first and second porous walls to produce respective fluid reaction products; the electrolyte solution and / or associated ions flow into the porous region of the or each porous wall having a discontinuous porous structure to react with the respective electrodes; A method is disclosed in which the first and second outlet chambers each hold a respective fluid reaction product for release, and the respective electrodes inhibit return flow of the fluid reaction product from the outlet chamber to the inlet chamber.

[0171] For the or each porous wall (electrode) having a discontinuous porous structure and having passive regions and electrocatalytic regions, the rate of each half-reaction of electrolysis in each electrocatalytic region may be greater than the rate of the half-reaction of electrolysis in each passive region.

[0172] The method may include controlling the inlet and / or outlet conditions of the electrolytic cell so that there is a pressure drop across each porous wall from the inlet chamber to the respective outlet chamber.

[0173] Electrolyte liquid may be admitted to each outlet chamber only through the respective porous walls.

[0174] The method may further include controlling operation of the electrolytic cell to maintain supercritical temperature and pressure conditions of the electrolyte liquid in the first porous wall and / or the second porous wall.

[0175] Controlling the operation of the electrolytic cell may include controlling the thermodynamics and / or flow rate of the electrolyte solution.

[0176] Controlling the thermodynamic and / or flow rate conditions may include controlling a flow control device to maintain a target inlet pressure and a target inlet temperature of the electrolyte liquid at the inlet, and / or controlling the current through the first and second electrodes and / or the voltage applied between the first and second electrodes.

[0177] For example, an electrolyte solution may be heated to a critical temperature corresponding to the supercritical condition of the electrolyte solution and provided at the or each respective porous wall (electrode) of the electrolytic cell.

[0178] Controlling the thermodynamic and / or flow rate conditions may include controlling a flow control device, such as a heater, such that the electrolyte solution is provided to the inlet at a temperature within 50°C (e.g., within 30°C or within 20°C) of a critical temperature, such as the critical temperature of the aqueous electrolyte solution of 374°C.

[0179] Controlling the thermodynamic and / or flow rate conditions may include controlling flow control devices, such as, for example, a compressor and / or one or more discharge valves associated with the electrolytic cell, to maintain a target inlet pressure. The target inlet pressure may be at least the critical pressure of the respective electrolyte solution. For example, the target inlet pressure may be at least 22 MPa for an aqueous electrolyte solution.

[0180] Supercritical temperature and pressure conditions of the electrolyte liquid can be maintained in the inlet chamber and in the first and second outlet chambers, and thermodynamic and / or flow rate conditions can be controlled such that the electrolyte liquid is provided to the inlet at supercritical conditions.

[0181] The supercritical temperature and pressure conditions can be, for aqueous electrolyte solutions, a pressure of at least 22 MPa and a temperature of at least 374° C. The supercritical conditions can be a pressure of 22 to 27 MPa and a temperature of 374° C. to 550° C., for example, 374° C. to 400° C.

[0182] The electrolytic cell may include a first release valve and a second release valve as defined above. The first release valve may maintain a first target pressure upstream of the valve, and the second release valve may maintain a second target pressure upstream of the valve. The first and second target pressures may differ such that there is a pressure drop across the porous wall that drives a bifurcated flow of electrolyte liquid from the inlet chamber through the porous wall and into the outlet chamber.

[0183] The controller may control the first and / or second discharge valves to maintain a target flow rate or composition from one or each of the first and second outlets based on flow rate data, upstream pressure data, and / or composition data received by the controller. The controller may control the first and / or second discharge valves to maintain a target flow rate ratio between the flow out of the first outlet and the flow out of the second outlet based on flow rate data and / or composition data received by the controller. The target flow rate ratio may correspond to the ratio of the total flow rate out of the first outlet to the total flow rate out of the second outlet, or the ratio of the flow rate of the first fluid reaction product out of the first outlet to the flow rate of the second fluid reaction product out of the second outlet.

[0184] The controller may, for example, determine whether an excessive amount of the second fluid reaction product is present in the outlet stream through the first outlet or may determine whether an excessive amount of the first fluid reaction product is present in the outlet stream through the second outlet based on composition data received at the controller for each outlet stream. The controller may control the first and / or second release valves to vary the flow rate through the porous wall of the electrolytic cell based on the determination.

[0185] The electrolyser may be operated to maintain thermodynamic and / or flow rate conditions such that the Reynolds number in the inlet chamber is 4000 or less, such as 2300 or less.

[0186] According to a fifth aspect, there is provided a method for producing a porous wall having a discontinuous porous structure of an electrolytic cell, comprising the steps of: providing a porous-walled body, the body being elongate along a longitudinal direction and having a thickness direction from a first side to a second side; removing material from the body to form a plurality of open areas, the open areas extending through the body at discrete locations, each open area being elongate along a path through the body having a longitudinal component; depositing an electrocatalyst composition on the body such that the composition flows into the open area; heating the body to perform a heat treatment operation in which the electrocatalytic component of the electrocatalyst composition forms porous regions at each location of the open regions, each porous region defining a respective network of flow paths through the body for permitting fluid to flow from a first side of the body to a second side of the body; A method is disclosed, comprising:

[0187] The porous wall may have any combination of the features disclosed above in relation to the porous wall of the first and second embodiments.

[0188] The method may further include a drying operation performed after depositing the electrocatalyst composition and before the heat treating operation to evaporate components of the electrocatalyst composition.

[0189] The drying operation may be performed to reduce the mass of the electrocatalyst composition retained on the body by 5-60%, e.g., 10-60%, 20-60%, 30-60%, or 30-50%. The drying operation may be performed to reduce the mass of the electrocatalyst composition corresponding to the mass of one or more solvents in the electrocatalyst composition as deposited. The drying operation may be performed at a temperature of 100°C-300°C, e.g., 150°C-250°C, e.g., about 200°C. The drying operation may be performed in an oven. The drying operation may be performed for 1-4 hours, e.g., 1-3 hours, e.g., about 2 hours.

[0190] The heat treatment operation can include heating the body to a target temperature of 150-1000°C.

[0191] The target temperature may be 150 to 1000°C, for example, 250 to 800°C, 300 to 600°C, or 300 to 450°C, for example, about 350°C.

[0192] Alternatively, the target temperature may be between 150 and 1500°C, such as between 150 and 1000°C, or between 600 and 1000°C, or between 800 and 1000°C, or between 900 and 1000°C, for example about 930°C.

[0193] The heat treatment operation may be a sintering operation in which the electrocatalyst components of the electrocatalyst composition are sintered to form porous regions (eg, sintered porous regions) at each location of the open regions.

[0194] The heat treatment operation may be a melting operation in which the electrocatalyst components of the electrocatalyst composition are melted to form porous regions (eg, molten porous regions) at each location of the open regions.

[0195] The heat-treating operation may be a bonding operation in which the electrocatalyst-containing particulates (e.g., electrocatalyst particles) of the electrocatalyst composition are bonded together to form porous regions (e.g., bonded porous regions) at each location of the open regions. Bonding the particles may include bonding the particles with a binder (e.g., a polymeric binder). Bonding the particles may include melting and / or curing the binder (e.g., a polymeric binder).

[0196] The heat treatment operation may be a chemical reaction operation in which electrocatalyst-containing particulates (e.g., electrocatalyst particles) of the electrocatalyst composition are bonded together through a chemical reaction to form porous regions (e.g., bonded porous regions) at each location of the open regions. For example, the chemical reaction operation may include forming a reaction product (e.g., an oxide) through a chemical reaction, where the reaction product bonds the electrocatalyst-containing particulates (e.g., electrocatalyst particles) together.

[0197] The heat treatment operation may include a temperature ramp-up stage in which the temperature is gradually increased to a target temperature. In the temperature ramp-up stage, the temperature ramp-up rate may be 0.5 to 5°C per minute, for example, 0.5 to 2°C per minute, for example, about 1°C per minute. The heat treatment operation may include a holding stage in which the temperature is maintained at the target temperature. The holding stage may last for 30 to 300 minutes, for example, 30 to 90 minutes, for example, about 60 minutes.

[0198] The heat treatment operation may include a two-stage heat treatment operation including heating the body to a first target temperature of 150-500°C and then heating to a second target temperature of 500-1000°C. The first target temperature may be 200-500°C, e.g., 250-450°C, or 300-500°C, e.g., about 300°C or about 350°C. The second target temperature may be 600-1000°C, e.g., 700-1000°C, or 800-1000°C, or 900-1000°C, or 900-950°C, e.g., about 930°C. The first stage of the heat treatment operation may include holding the body at the first target temperature for 2-10 hours, e.g., 4-8 hours, e.g., about 6 hours. A second stage of the heat treating operation may include holding the body at the second target temperature for 30 to 300 minutes, such as 30 to 90 minutes, for example about 60 minutes.

[0199] The first stage may be performed to pyrolyze or burn off non-electrocatalytic components of the electrocatalyst composition, such as the binder component of the electrocatalyst composition. Thus, the first stage may be performed in an oxidizing atmosphere. Thus, the first stage of the heat treatment operation can be considered a pyrolysis operation.

[0200] The second stage may be performed to aggregate (e.g., sinter) the electrocatalyst-containing particulates (e.g., electrocatalyst particles) together. Thus, the second stage may be performed in an inert (or reducing) atmosphere, such as an argon atmosphere or a nitrogen / hydrogen atmosphere. Thus, it can be considered a second aggregation (e.g., sintering) operation of the heat treatment operation.

[0201] The second stage of the heat treatment operation may be performed simultaneously with, include, or be another heat treatment operation, such as a post-weld heat treatment operation (e.g., a stress relief heat treatment operation).

[0202] The method may be a method for producing a porous wall of an electrolytic cell according to the second aspect.

[0203] The electrocatalyst composition has a viscosity of about 1 Pa·s to about 30 Pa·s when applied to the body.

[0204] The electrocatalyst composition may have a (i.e., dynamic) viscosity of about 1 Pa·s or greater, e.g., about 2 Pa·s or greater, or about 4 Pa·s or greater, or about 5 Pa·s or greater, or about 6 Pa·s or greater, or about 8 Pa·s or greater, or about 10 Pa·s or greater, or about 12 Pa·s or greater, or about 14 Pa·s or greater, or about 16 Pa·s or greater, or about 18 Pa·s or greater, or about 20 Pa·s or greater, or about 21 Pa·s or greater, or about 22 Pa·s or greater, or about 23 Pa·s or greater, or about 24 Pa·s or greater, or about 25 Pa·s or greater. The electrocatalyst composition may have a (i.e., dynamic) viscosity of about 30 Pa·s or less, e.g., about 28 Pa·s or less, or about 26 Pa·s or less, or about 25 Pa·s or less, or about 24 Pa·s or less, or about 23 Pa·s or less, or about 22 Pa·s or less, or about 21 Pa·s or less, or about 20 Pa·s or less, or about 19 Pa·s or less, or about 18 Pa·s or less, or about 17 Pa·s or less, or about 16 Pa·s or less, or about 14 Pa·s or less, or about 12 Pa·s or less, or about 10 Pa·s or less, or about 8 Pa·s or less. The electrocatalyst composition may have a viscosity of from about 1 Pa·s to about 30 Pa·s, for example, from about 1 Pa·s to about 28 Pa·s, or from about 1 Pa·s to about 26 Pa·s, or from about 1 Pa·s to about 25 Pa·s, or from about 1 Pa·s to about 24 Pa·s, or from about 1 Pa·s to about 23 Pa·s, or from about 1 Pa·s to about 22 Pa·s, or from about 1 Pa·s to about 21 Pa·s, or from about 1 Pa·s to about 20 Pa·s, or from about 1 Pa·s to about 18 Pa·s, or from about 1 Pa·s to about 16 Pa·s, or from about 1 Pa·s to about 14 Pa·s, or from about 1 Pa·s to about 12 Pa·s, or from about 1 Pa·s to about 10 Pa·s. a·s, or about 1 Pa·s to about 8 Pa·s, or about 2 Pa·s to about 30 Pa·s, for example about 2 Pa·s to about 28 Pa·s, or about 2 Pa·s to about 26 Pa·s, or about 2 Pa·s to about 25 Pa·s, or about 2 Pa·s to about 24 Pa·s, or about 2 Pa·s to about 23 Pa·s, or about 2 Pa·s to about 22 Pa·s, or about 2 Pa·s to about 21 Pa·s, or about 2 Pa·s to about 20 Pa·s, or about 2 Pa·s to about 18 Pa·s, or about 2 Pa·s to about 16 Pa·s, or about 2 Pa·s to about 14 Pa·s, or about 2 Pa·s to about 12 Pa·s,or about 2 Pa·s to about 10 Pa·s, or about 2 Pa·s to about 8 Pa·s, or about 4 Pa·s to about 30 Pa·s, for example about 4 Pa·s to about 28 Pa·s, or about 4 Pa·s to about 26 Pa·s, or about 4 Pa·s to about 25 Pa·s, or about 4 Pa·s to about 24 Pa·s, or about 4 Pa·s to about 23 Pa·s, or about 4 Pa·s to about 22 Pa·s, or about 4 Pa·s to about 21 Pa·s, or about 4 Pa·s to about 20 Pa·s, or about 4 Pa·s to about 18 Pa·s, or about 4 Pa·s to about 16 Pa·s, or about 4 Pa·s to about 14 Pa·s, or about 4 Pa·s to about 12 Pa·s, or about 4 Pa·s to about 10 Pa·s, or about 4 Pa·s to about 8 Pa·s, or about 5 Pa·s to about 30 Pa·s, for example about 5 Pa·s to about 28 Pa·s, or about 5 Pa·s to about 26 Pa·s, or about 5 Pa·s to about 25 Pa·s, or about 5 Pa·s to about 24 Pa·s, or about 5 Pa·s to about 23 Pa·s, or about 5 Pa·s to about 22 Pa·s, or about 5 Pa·s to about 21 Pa·s, or about 5 Pa·s to about 20 Pa·s, or about 5 Pa·s to about 18 Pa·s, or about 5 Pa·s to about 16 Pa·s, or about 5 Pa·s to about 14 Pa·s, or about 5 Pa·s to about 12 Pa·s, or about 5 Pa·s to about 10 Pa·s, or about 5 Pa·s to about 8 Pa·s, or about 6 Pa·s to about 30 Pa·s, for example, about 6 Pa·s to about 28 Pa·s, or about 6 Pa·s to about 26 Pa·s, or about 6 Pa·s to about 25 Pa·s, or about 6 Pa·s to about 24 Pa·s, or about 6 Pa·s to about 23 Pa·s, or about 6 Pa·s to about 22 Pa·s, or about 6 Pa·s to about 21 Pa·s, or about 6 Pa·s to about 20 Pa·s, or about 6 Pa·s to about 18 Pa·s, or about 6 Pa·s to about 16 Pa·s, or about 6 Pa·s to about 14 Pa·s, or about 6 Pa·s to about 12 Pa·s, or about 6 Pa·s to about 10 Pa·s, or about 6 Pa·s to about 8 Pa·s, or about 8 Pa·s to about 30 Pa·s, for example about 8 Pa·s to about 28 Pa·s, or about 8 Pa·s to about 26 Pa·s, or about 8 Pa·s to about 25 Pa·s, or about 8 Pa·s to about 24 Pa·s, or about 8 Pa·s to about 23 Pa·s, or about 8 Pa·s to about 22 Pa·s, or about 8 Pa·s to about 21 Pa·s,or about 8 Pa·s to about 20 Pa·s, or about 8 Pa·s to about 18 Pa·s, or about 8 Pa·s to about 16 Pa·s, or about 8 Pa·s to about 14 Pa·s, or about 8 Pa·s to about 12 Pa·s, or about 8 Pa·s to about 10 Pa·s, or about 8 Pa·s to about 8 Pa·s, or about 10 Pa·s to about 30 Pa·s, or about 10 Pa·s to about 28 Pa·s, or about 20 Pa·s to about 26 Pa·s, or or about 10 Pa·s to about 25 Pa·s, or about 10 Pa·s to about 24 Pa·s, or about 10 Pa·s to about 23 Pa·s, or about 10 Pa·s to about 22 Pa·s, or about 10 Pa·s to about 21 Pa·s, or about 10 Pa·s to about 20 Pa·s, or about 10 Pa·s to about 18 Pa·s, or about 10 Pa·s to about 16 Pa·s, or about 10 Pa·s to about 14 Pa·s, or about 10 Pa·s to about 1 2 Pa·s, or about 12 Pa·s to about 30 Pa·s, or about 14 Pa·s to about 30 Pa·s, or about 16 Pa·s to about 30 Pa·s, or about 18 Pa·s to about 30 Pa·s, or about 20 Pa·s to about 30 Pa·s, or about 21 Pa·s to about 30 Pa·s, or about 22 Pa·s to about 30 Pa·s, or about 23 Pa·s to about 30 Pa·s, or about 24 Pa·s to about 30 Pa·s, or about 25 The electrocatalyst composition may have a (i.e., dynamic) viscosity of from about 16 Pa·s to about 30 Pa·s, or from about 16 Pa·s to about 25 Pa·s, or from about 18 Pa·s to about 25 Pa·s, or from about 20 Pa·s to about 25 Pa·s, or from about 16 Pa·s to about 23 Pa·s, or from about 18 Pa·s to about 23 Pa·s, or from about 20 Pa·s to about 23 Pa·s, or from about 16 Pa·s to about 20 Pa·s, or from about 18 Pa·s to about 20 Pa·s. The (i.e., dynamic) viscosity of the electrocatalyst composition may be measured at 25°C according to, for example, ISO 3104:2020.

[0205] The electrocatalyst composition may comprise a mixture of electrocatalyst and liquid precipitate when applied to the body.

[0206] An electrocatalyst composition is a composition that includes (e.g., consists essentially of, consists of, or is) an electrocatalyst for each half-reaction of the electrolysis. For example, an electrocatalyst composition may include (e.g., may consist essentially of, or may consist of) a mixture of an electrocatalyst for each half-reaction of the electrolysis and a liquid.

[0207] The electrocatalyst composition may comprise (e.g., may be, consist essentially of, or consist of) a slurry including an electrocatalyst and a liquid for each half-reaction of the electrolysis.

[0208] The electrocatalyst composition may comprise (e.g., may be, consist essentially of, or consist of) a suspension of an electrocatalyst for each half-reaction of the electrolysis in a liquid.

[0209] The electrocatalyst may be provided in the mixture in the form of particulates.

[0210] The electrocatalyst composition may comprise (e.g., be, consist essentially of, or consist of) a colloidal suspension (e.g., of particulates in a liquid). For example, the electrocatalyst composition may comprise (e.g., be, consist essentially of, or consist of) a sol (i.e., a solid-liquid colloidal suspension) containing an electrocatalyst for each half-reaction of the electrolysis, a conductive ink (i.e., a suspension of conductive electrocatalyst particles in a liquid), or a paste (i.e., a solid-liquid suspension with a sufficiently high solids content that the suspension behaves as a solid in response to low applied stress).

[0211] The electrocatalyst may be any suitable electrocatalyst described herein.

[0212] The particle size characteristics of electrocatalyst particles can be measured in a well-known manner by laser scattering techniques (e.g., standard ISO 13320-1). In this technique, the size of particles in powders, suspensions, and emulsions is measured using the diffraction of a laser beam, based on the application of Mie theory. For example, machines available from Microtrac MRB provide measurements and plots of the cumulative percentage by volume of particles whose size, referred to in the art as "equivalent spherical diameter (esd)," is less than a given esd value. The mean particle size d 50 is the volume of the particle that is 50% of its d 50 The particle esd determined in this manner has an equivalent spherical diameter less than the value d. 99 The value is the value where 99% of the particle's volume is at its d 99 The value of esd is determined in the same manner for particles having an equivalent spherical diameter less than the value.

[0213] The electrocatalyst fine particles have a diameter of about 100 nm or more, for example, about 500 nm or more, or about 1 μm or more, or about 4 μm or more, or about 5 μm or more, or about 8 μm or more, or about 10 μm or more. 50 The electrocatalyst particulates may have a d of about 100 μm or less, for example, about 75 μm or less, or about 50 μm or less, or about 25 μm or less, or about 20 μm or less. 50The electrocatalyst fine particles may have a size of about 100 nm to about 100 μm, for example, about 500 nm to about 100 μm, or about 750 nm to about 100 μm, or about 1 μm to about 100 μm, or about 10 μm to about 100 μm, or about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 750 nm to about 50 μm, or about 1 μm to about 50 μm, or about 10 μm to about 50 μm, or about 500 nm to about 20 μm, or about 750 nm to about 20 μm, or about 1 μm to about 20 μm, or about 10 μm to about 20 μm, or about 500 nm nm to about 50 μm, or about 750 nm to about 50 μm, or about 1 μm to about 50 μm, or about 10 μm to about 50 μm, or about 500 nm to about 25 μm, or about 750 nm to about 25 μm, or about 1 μm to about 25 μm, or about 10 μm to about 25 μm, or about 500 nm to about 20 μm, or about 750 nm to about 20 μm, or about 1 μm to about 20 μm, or about 10 μm to about 20 μm, or about 500 nm to about 15 μm, or about 750 nm to about 15 μm, or about 1 μm to about 15 μm, or about 10 μm to about 15 μm 50 may have

[0214] The electrocatalyst fine particles have a diameter of about 1 μm or more, for example, about 10 μm or more, or about 20 μm or more, or about 30 μm or more, or about 35 μm or more. 99 The electrocatalyst particulates may have a d of about 150 μm or less, e.g., about 100 μm or less, or about 75 μm or less, or about 50 μm or less, or about 45 μm or less, or about 40 μm or less. 99The electrocatalyst fine particles may have a size of about 1 μm to 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 1 μm to about 45 μm, or about 1 μm to about 50 μm, or about 10 μm to about 150 μm, or about 10 μm to about 100 μm, or about 10 μm to about 75 μm, or about 10 μm to about 50 μm, or about 10 μm to about 45 μm, or about 10 μm to about 40 μm, or about 20 μm to about 150 μm, or about 20 μm to about 100 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 20 μm to about 45 μm, or about 20 μm to about 40 μm, or about 30 μm to about 150 μm, or about 30 μm to about 100 μm, or about 30 μm to about 75 μm, or about 30 μm to about 50 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm 99 may have

[0215] d 50 and / or d 99 Smaller particle sizes may facilitate better penetration of the electrocatalyst composition into open areas, as evidenced by lower values ​​of .

[0216] For example, electrocatalyst particles can be prepared from noble metals (i.e., Ru, Rh, Pd, Os, Ir, Pt, Au, Ag, Re), d-block transition metals (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, R, Os, Ir, Pt, Au, Hg, Rf, Db, S, Rh, Hs, Mt, Ds, Rg, Cn), f-block lanthanides (i.e., La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), rare earth metals (i.e., The electrocatalyst fine particles may comprise (e.g., consist essentially of, or consist of) one or more elements selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), platinum group metals (i.e., Ru, Rh, Pd, Os, Ir, Pt), P, S, C, and / or combinations thereof, and the electrocatalyst fine particles have a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm. 50 , and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 It has.

[0217] The electrocatalyst particulates may include particles comprising (e.g., consisting essentially of, or consisting of) Co, Fe, Ir, Li, Ni, P, S, Ti, Zn, and / or combinations thereof, and the electrocatalyst particulates may have a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm, or about 8 μm to about 16 μm. 50, and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 It has.

[0218] The electrocatalyst particulates may include particles comprising (e.g., consisting essentially of, or consisting of) Ce, Co, Fe, Ho, Ir, Mo, Ni, Pd, Pt, Ru, Sm, W, and / or combinations thereof, and the electrocatalyst particulates have a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm. 50 , and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 It has.

[0219] The electrocatalyst particulates may include particles comprising (e.g., consisting essentially of, or consisting of) Ni, Fe, Co, P, S, and / or combinations thereof, and the electrocatalyst particulates may have a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm, or about 4 μm to about 10 μm. 50, and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 It has.

[0220] The electrocatalyst particulates may include particles comprising (e.g., consisting essentially of, or consisting of) Pt, Ir, Pd, Ni, Mo, and / or combinations thereof, and the electrocatalyst particulates have a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm. 50 , and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 It has.

[0221] In some examples, the electrocatalyst particulates include particles comprising (e.g., consisting essentially of, or consisting of) Ni (e.g., elemental Ni) or Pt (e.g., elemental Pt), and the electrocatalyst particulates have a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm. 50, and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 It has.

[0222] In some examples, the electrocatalyst particulates include particles comprising (e.g., consisting essentially of, or consisting of) Ni (e.g., elemental Ni), and the electrocatalyst particulates have a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm. 50 , and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 It has.

[0223] In some examples, the electrocatalyst particulates include particles comprising (e.g., consisting essentially of, or consisting of) Pt (e.g., elemental Pt), and the electrocatalyst particulates have a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm. 50 , and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 It has.

[0224] In some examples, the electrocatalyst particulate is a Ni-containing particulate, and the electrocatalyst particulate has a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm. 50 , and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 The Ni-containing particulates may include (eg, consist essentially of, or consist of) particles of Ni (eg, elemental Ni) or a Ni-based alloy.

[0225] In some examples, the electrocatalyst-containing particles are Ni particles consisting essentially of Ni particles, and the electrocatalyst particles have a diameter of about 100 nm to about 100 μm, e.g., about 500 nm to about 100 μm, or about 500 nm to about 50 μm, or about 1 μm to about 50 μm, or about 1 μm to about 25 μm. 50 , and about 1 μm to about 150 μm, for example, about 1 μm to about 75 μm, or about 1 μm to about 50 μm, or about 10 μm to about 75 μm, or about 10 μm to about 75 μm, or about 20 μm to about 75 μm, or about 20 μm to about 50 μm, or about 30 μm to about 75 μm, or about 30 μm to about 45 μm, or about 30 μm to about 40 μm. 99 It has.

[0226] The electrocatalyst-containing particulates may have (e.g., substantially) any suitable particle shape (i.e., morphology), such as spherical, spheroidal, acicular or needle-like, fibrous, plate-like, or flake-like. In some examples, the electrocatalyst-containing particulates have a flake-like particle shape. In some examples, the electrocatalyst-containing particulates comprise (e.g., consist essentially of, or consist of) electrocatalyst flakes, such as, for example, metal or metal alloy flakes (e.g., Ni or Ni alloy flakes).

[0227] An appropriate liquid may be selected based on manufacturing constraints such as the properties of the electrocatalyst particulates, the size of the open area, and / or the heating temperature.

[0228] The liquid may be polar or non-polar.

[0229] The liquid may be aqueous (e.g., water-based), that is, the liquid may include (e.g., consist essentially of, consist of, or be) water.

[0230] The liquid may be organic. The liquid may include (e.g., consist essentially of, consist of, or be) one or more organic species, such as, for example, hydrocarbons.

[0231] The liquid may include (e.g., may consist essentially of, consist of, or be) one or more alcohols, esters, acetates, acetate esters, ether acetates, and / or acids.

[0232] The liquid may, for example, comprise (e.g., consist essentially of, consist of, or be) one or more solvents, e.g., one or more polar solvents or one or more non-polar solvents, e.g., one or more organic solvents.

[0233] In some examples, the liquid comprises (eg, consists essentially of, consists of, or is) a non-polar ester (eg, a non-polar ester solvent).

[0234] In some examples, the liquid comprises (e.g., consists essentially of, consists of, or is) a reaction product of a carboxylic acid and an alcohol, for example, the alcohol comprises an alkoxy alcohol. In some examples, the liquid comprises (e.g., consists essentially of, consists of, or is) an acetate ester or ether acetate. In some examples, the liquid comprises (e.g., consists essentially of, consists of, or is) 2-butoxyethyl acetate.

[0235] The electrocatalyst composition may include a binder, for example, a polymeric binder. The polymeric binder may be a thermoplastic binder or a thermosetting binder (e.g., a resin). A thermoplastic binder is a polymeric binder that melts or becomes flexible at elevated temperatures and solidifies upon cooling. A thermosetting binder (e.g., a resin) is a polymeric binder that irreversibly hardens (i.e., cures) upon heating, exposure to radiation, and / or exposure to an appropriate catalyst. The binder may be dispersed or dissolved in a liquid.

[0236] The electrocatalyst composition may include one or more additives, such as viscosity or rheology modifiers, tackifiers, plasticizers, pigments, etc. For example, the electrocatalyst composition may include carbon black.

[0237] A suitable electrocatalyst composition may be Conductive Ink 116-25 available from Creative Materials Inc. (Massachusetts, USA). The viscosity of Conductive Ink 116-25 can be adjusted as needed by dilution with Solvent 112-19, Solvent 102-03, or Solvent 113-12, also available from Creative Materials Inc. (Massachusetts, USA).

[0238] The method according to the fifth aspect may be for providing a porous wall with a discontinuous porous structure in a flow configuration according to the first aspect or in an electrolytic cell according to the second aspect.

[0239] According to a sixth aspect, there is provided a method for producing a porous wall having a discontinuous porous structure of an electrolytic cell, comprising the steps of: forming a porous wall by an additive manufacturing process, the porous wall comprising: a body having a first side and a second side, the body being elongate along a longitudinal direction and having a thickness direction from the first side to the second side; a plurality of porous regions extending through the body at discrete locations to allow fluid to flow from the first side to the second side; each porous region defining a respective network of flow channels through the body; each porous region is elongate along a path through the body having a longitudinal component; A method is disclosed in which an additive manufacturing process is controlled to vary the porosity of the porous walls during formation such that the porous region is formed with a higher open porosity than the body.

[0240] Thus, each porous region can interface with the body at a respective boundary that surrounds the porous region and is defined by the change in porosity between the body and the porous region.

[0241] The porous region and the body may have a common material composition.

[0242] The material composition may include an electrocatalyst, such that the porous wall includes an electrocatalyst region comprising at least the porous region. The electrocatalyst may be or have any of the properties as described above with respect to the fifth embodiment. Regions of the body outward from the porous region may also include an electrocatalyst, but they may not be configured to contact the electrolyte liquid in use (e.g., recessed portions of the wall not exposed to fluid flow).

[0243] The method can further include providing a passivating coating on the first side of the body configured to be less electrocatalytically active than the electrocatalytic region of the porous wall that includes the porous region.

[0244] The method according to the sixth aspect may be for providing a porous wall with a discontinuous porous structure in a flow configuration according to the first aspect or in an electrolytic cell according to the second aspect.

[0245] According to a seventh aspect, a flow arrangement for an electrolytic cell is disclosed, comprising: first and second porous walls corresponding to first and second electrodes of the electrolytic cell; an inlet chamber disposed between the first and second porous walls and configured to receive an electrolyte liquid through an inlet; and first and second outlet chambers for retaining respective fluid reaction products of the electrolysis, separated from the inlet chamber by the first and second porous walls, respectively.

[0246] The or each porous wall may comprise a body having an inlet side adjacent the inlet chamber and an outlet side adjacent the respective outlet chamber, the body being elongate along a longitudinal direction and having a thickness direction from the inlet side to the outlet side.

[0247] In the flow configuration according to the seventh aspect, the porous wall may not have a discontinuous porous structure as described elsewhere herein.

[0248] For example, the or each porous wall may include a plurality of channels extending through the body.

[0249] Each channel can be elongate along a path through the body having a longitudinal component. Each channel can be elongate along a path through the body that defines a path angle of between 20° and 80° with respect to the longitudinal direction.

[0250] The path angle may be between 25° and 75°, for example, between 30° and 70°, between 35° and 70°, between 40° and 70°, for example, between 50° and 70°.

[0251] Each channel may have an average path diameter of 25 to 250 μm, e.g., 50 to 250 μm, 50 to 150 μm, 70 to 150 μm, or about 120 μm. The average diameter may be the average cross-sectional diameter along the length of the channel.

[0252] Each channel may have a midpoint diameter of 25-250 μm, e.g., 25-100 μm, 25-80 μm, or 25-50 μm. The midpoint diameter may be the diameter halfway along the length of the channel.

[0253] Each channel may have an entrance diameter of 25-250 μm, for example, 50-250 μm, 50-150 μm, 70-150 μm, or about 120 μm. The entrance diameter may be the diameter of the channel at the entrance side of its respective wall.

[0254] Each channel may have an outlet diameter of 25-250 μm, for example, 50-250 μm, 50-150 μm, 70-150 μm, or about 120 μm. The outlet diameter may be the diameter of the channel at the outlet side of its respective wall.

[0255] Each porous region is 10,000 to 250,000 μm 2 , for example, 15,000 to 250,000 μm 2 , 15,000~150,000μm 2 , 20,000~150,000μm2 , 50,000~150,000μm 2 , or approximately 100,000 μm 2 Each cross-sectional area can be determined as the volume of the channel divided by the extent of the channel along the thickness direction.

[0256] The or each porous wall body may include or be defined by a porous medium, for example, the porous medium may define an inlet side and an outlet side of the body over a continuous longitudinal extent of the body over which the porous wall is porous for fluid flow between the inlet chamber and the respective outlet chamber.

[0257] The flow arrangement according to the seventh aspect may have any combination of features as described above with respect to the first aspect and / or with respect to the second to sixth aspects, except where such features are mutually exclusive.

[0258] The controllers described herein may include a processor. The controller and / or processor may include any suitable circuitry for implementing the methods described herein and illustrated in the figures. The controller or processor may include at least one application-specific integrated circuit (ASIC), at least one field-programmable gate array (FPGA), single or multi-processor architecture, sequential (von Neumann) / parallel architecture, at least one programmable logic controller (PLC), at least one microprocessor, at least one microcontroller, and / or central processing unit (CPU) for implementing the methods and / or the described functions for which the controller or processor is configured.

[0259] The controller may include, or the processor may be in communication with, one or more memories that store the data described herein and / or store machine-readable instructions (e.g., software) for implementing the processes and functions described herein (e.g., determining parameters and executing control routines).

[0260] The memory may be any suitable non-transitory computer-readable storage medium, one or more data storage devices, and may include a hard disk and / or solid-state memory (such as a flash memory). In some examples, the computer-readable instructions may be transferred to the memory via a wireless signal or via a wired signal. The memory may be a permanent, non-removable memory or a removable memory (such as a Universal Serial Bus (USB) flash drive). The memory may store a computer program including computer-readable instructions that, when read by a processor or controller, cause the processor or controller to implement the methods described herein and / or illustrated in the figures. The computer program may be software or firmware, or a combination of software and firmware.

[0261] Except where mutually exclusive, features described in relation to any one of the above embodiments may be applied mutatis mutandis to any other embodiment. Further, except where mutually exclusive, any feature described herein may be applied to any embodiment and / or may be combined with any other feature described herein.

[0262] The present invention will now be described, by way of example only, with reference to the accompanying drawings. [Brief explanation of the drawings]

[0263] [Figure 1a]FIG. 1 is a cross-sectional view of an exemplary flow configuration of an electrolytic cell. [Figure 1b] 1A-1C are cross-sectional views of exemplary configurations of porous walls in flow configurations. [Figure 1c] 1A-1C are cross-sectional views of exemplary configurations of porous walls in flow configurations. [Figure 1d] 1A-1C are cross-sectional views of exemplary configurations of porous walls in flow configurations. [Figure 2a] 10A-10C are cross-sectional views of further exemplary configurations of porous walls including passive regions. [Figure 2b] 10A-10C are cross-sectional views of further exemplary configurations of porous walls including passive regions. [Figure 2c] 10A-10C are cross-sectional views of further exemplary configurations of porous walls including passive regions. [Figure 3a] 1 is a flow diagram of a method for manufacturing a porous wall. [Figure 3b] FIG. 1 is a schematic diagram of an applicator for an electrocatalyst composition. [Figure 4a] FIG. 1 shows SEM (scanning electron microscope) images of one side of a porous wall at various levels of fabrication. [Figure 4b] FIG. 1 shows SEM (scanning electron microscope) images of one side of a porous wall at various levels of fabrication. [Figure 4c] FIG. 1 shows SEM (scanning electron microscope) images of one side of a porous wall at various levels of fabrication. [Figure 4d] FIG. 1 shows SEM (scanning electron microscope) images of one side of a porous wall at various levels of fabrication. [Figure 5] 1 is a flow diagram of a method for manufacturing a porous wall. [Figure 6] 6 shows an image of a cross section of an exemplary porous wall as produced by the method of FIG. 5. [Figure 7] FIG. 1 is a schematic diagram of the geometric arrangement of an axisymmetric flow simulation model. [Figure 8a] FIG. 10 shows contour plots of fluid reaction product and electrolyte concentrations in a flow simulation. [Figure 8b]FIG. 10 shows contour plots of fluid reaction product and electrolyte concentrations in a flow simulation. [Figure 8c] FIG. 10 shows contour plots of fluid reaction product and electrolyte concentrations in a flow simulation. [Figure 8d] 8a-8c show mass flow and species crossover results for flow simulations corresponding to FIGS. 8a-8c at selected flow rates. [Figure 8e] 8a-8c show mass flow and species crossover results for flow simulations corresponding to FIGS. 8a-8c at selected flow rates. [Figure 9a] FIG. 1 shows mass flow and species crossover results from selected parametric studies. [Figure 9b] FIG. 1 shows mass flow and species crossover results from selected parametric studies. [Figure 9c] FIG. 1 shows mass flow and species crossover results from selected parametric studies. [Figure 9d] FIG. 1 shows mass flow and species crossover results from selected parametric studies. [Figure 9e] FIG. 1 shows mass flow and species crossover results from selected parametric studies. [Figure 9f] FIG. 1 shows mass flow and species crossover results from selected parametric studies. [Figure 10a] FIG. 1 shows a matrix of flow simulation results from a parametric study of the independent variables of porosity and pore angle. [Figure 10b] FIG. 1 shows a matrix of flow simulation results from a parametric study of the independent variables of porosity and pore angle. [Figure 10c] FIG. 1 shows a matrix of flow simulation results from a parametric study of the independent variables of porosity and pore angle. [Figure 10d] FIG. 1 shows a matrix of flow simulation results from a parametric study of the independent variables of porosity and pore angle. [Figure 11] 1b is a schematic diagram of an example of an electrolysis installation comprising an electrolytic cell according to FIG. 1a; [Figure 12] 1 is a flow diagram of a method for controlling an electrolytic cell. [Figure 13] FIG. 1 is an optical micrograph (377.5x magnification) of the surface of a porous electrode formed by laser drilling channels into the wall of an alumina-coated Inconel® alloy 625 tube. [Figure 14] FIG. 13 shows an image of a cross section of the porous electrode shown in FIG. 12 obtained by X-ray computed tomography (XCT). [Figure 15(a)] FIG. 14 is an enlarged view of a portion of the image shown in FIG. [Figure 15(b)] FIG. 1 is an optical micrograph (377.5x magnification) of the surface of a porous electrode formed by laser drilling channels into the wall of an alumina-coated Inconel® alloy 625 tube. [Figure 16(a)] FIG. 2 is a representative gas chromatogram of cathode gas obtained from an electrolyzer according to the invention, characterizing (from left to right) three peaks related to hydrogen, oxygen and nitrogen content. [Figure 16(b)] FIG. 2 is a representative gas chromatogram of the anode gas obtained from an electrolyzer according to the invention, characterizing (from left to right) three peaks associated with hydrogen, oxygen and nitrogen content. [Figure 17(a)] FIG. 1 is a representative gas chromatogram of an oxygen calibration gas. [Figure 17(b)] FIG. 1 shows representative gas chromatograms of hydrogen and nitrogen calibration gases. [Figure 18(a)] FIG. 1 shows plots of cumulative intrusion volume versus pore size obtained by mercury porosimetry for three sample porous electrodes. [Figure 18(b)] FIG. 1 shows plots of cumulative volume versus pore size obtained by mercury porosimetry for three sample porous electrodes. [Figure 18(c)]FIG. 1 shows plots of log differential intrusion versus pore size obtained by mercury porosimetry for three sample porous electrodes. [Figure 18(d)] FIG. 1 shows plots of cumulative intrusion volume versus pore size obtained by mercury porosimetry for five sample porous electrodes. [Figure 18(e)] FIG. 1 shows plots of cumulative volume versus pore size obtained by mercury porosimetry for five sample porous electrodes. [Figure 18(f)] FIG. 1 shows plots of log differential intrusion versus pore size obtained by mercury porosimetry for five sample porous electrodes. [Figure 19] FIG. 1 shows three SEM images (a), (b) and (c) of different areas of a sintered electrocatalyst material taken at 1000x magnification. DETAILED DESCRIPTION OF THE INVENTION

[0264] Figure 1a shows a schematic of an exemplary flow configuration 100 of an electrolytic cell having a first porous wall and a second porous wall, while Figures 1b-1d show exemplary configurations of the porous walls.

[0265] The flow configuration 100 includes an inlet chamber 102, in this example an annular chamber 102 having a central longitudinal direction A, elongated along the longitudinal direction A. The inlet chamber 102 is configured to receive an annular inlet flow at an annular inlet 101. In this example, the various structures are axisymmetric about the longitudinal direction A, which may be referred to as the longitudinal direction A of the flow configuration.

[0266] The flow configuration 100 further comprises a first outlet chamber 130 and a second outlet chamber 140 separated from the inlet chamber by a first porous wall 110 and a second porous wall 120, respectively. In this example, the first outlet chamber 130 is an inner central chamber radially within and surrounded by the inlet chamber 102, and the second outlet chamber 140 is an outer annular chamber radially outside and surrounding the inlet chamber 102. Each of the first and second outlet chambers is concentric with and elongated along the longitudinal direction A.

[0267] The flow arrangement is generally elongate and has a proximal end corresponding to an inlet 101 for receiving a fluid flow, and a distal end (described below) corresponding to an outlet for discharging the flow. Various components of the flow arrangement (and of associated devices such as electrolyzers) may be described with reference to their proximal and distal ends according to the same frame of reference.

[0268] The inlet chamber 102 is open at its proximal end at the inlet 101 and closed at its distal end 104. The flow arrangement 10 is therefore configured such that the only entrance to the inlet chamber 102 is the inlet 101 and the only route for flow out of the inlet chamber 102 is via one or both of the porous walls 110, 120.

[0269] First outlet chamber 130 is closed at a proximal end and defines a first outlet 132 at or toward its distal end. First outlet chamber 130 may extend beyond the longitudinal extent of first porous wall 110 (or beyond the longitudinal extent of first porous wall 110 configured to provide flow to the first outlet chamber), as shown schematically by the extended lines in FIG. 1 . First outlet chamber 130 is configured to receive flow only through first porous wall 110 and to discharge flow only through first outlet 132.

[0270] The first outlet chamber 130 is shown in this example as cylindrical, but may have any other suitable configuration, for example, may be annular or conical, or non-axisymmetric, as further described below.

[0271] Second outlet chamber 140 is closed at a proximal end and defines a second outlet 142 at or towards its distal end. Second outlet chamber 140 may extend beyond the longitudinal extent of second porous wall 120 (or beyond the longitudinal extent of a second porous wall configured to provide flow to the second outlet chamber), as shown schematically by the extended lines in FIG.

[0272] Although the second outlet chamber 140 is shown as annular in this example, it may have any other suitable configuration, for example, a non-cylindrical radially outer wall or a non-axisymmetric configuration, as further described below.

[0273] The exemplary flow configuration 10 further includes an inlet flow distributor 150 configured to provide an annular fluid flow to the annular inlet 101 of the inlet chamber 102. In this example, the flow distributor 150 has a diverging conical profile configured to direct the fluid around a flow divider 152. The flow distributor has a port 154 for coupling to a fluid source. In variations, the flow distributor 150 may take any suitable shape or configuration, for example, it may have a cylindrical outer wall, and there may be a conical flow divider within the flow distributor to direct the flow toward the annular inlet 101.

[0274] The first porous wall 110 and the second porous wall 120 are each elongate along a respective longitudinal direction, which in this example is the longitudinal direction A of the flow configuration 100. The first porous wall 110 and the second porous wall 120 each have a thickness direction from an inlet side adjacent the inlet chamber 102 and an outlet side adjacent the respective outlet chambers 130, 140.

[0275] An example of flow through the flow configuration will now be described. Fluid (e.g., electrolyte solution) is received from a fluid source (e.g., a supply of electrolyte solution) at port 154 and flows through flow distributor 150 to inlet 101 to inlet chamber 102. Inlet chamber 102 has no outlets other than through porous walls 110, 120. In use, branch flows are established from inlet chamber 102 to respective outlet chambers 130, 140, with each branch flow passing through a respective porous wall 110, 120. Each outlet chamber 130, 140 has only a single inlet in the form of a respective porous wall 110, 120 and has an outlet 132, 142 (e.g., a single outlet). Thus, within each outlet chamber, flow passes from the respective porous wall 110, 120 generally longitudinally along the outlet chamber and is discharged at the outlet.

[0276] Further features regarding mechanisms for inhibiting backflow through the porous walls (i.e., from the outlet chambers 130, 140 to the inlet chamber 102) are described below. Exemplary specifications for flow configurations in electrolytic cells are described below following the discussion related to the electrolysis reactions.

[0277] As shown in FIG. 1b, in a first example, the first porous wall 110 and the second porous wall 120 each have an isotropic porous configuration and are formed from an isotropic porous medium having a porosity that allows fluid to flow therethrough from the inlet side to the outlet side. The term "porosity" as used herein refers to the open porosity of a component (e.g., the volume fraction open to fluid flow therethrough). Suitable tests or procedures for determining porosity are described elsewhere herein. By way of example, FIG. 1b illustrates an example of flow from the inlet chamber 102 through the first porous wall 110 to the first outlet chamber 130, but is equally applicable to and representative of flow from the inlet chamber 102 through the second porous wall 120 to the second outlet chamber 140.

[0278] As used herein, the expression "isotropic porous medium" refers to a porous medium in which the porosity does not vary by more than an order of magnitude according to the direction of measurement. The porosity may vary locally and may be defined, for example, by a structure of fused granular or particulate elements having a distribution of characteristic dimensions, with open spaces defined between them, but with respect to their arrangement, there is no directional structure that significantly biases (e.g., by an order of magnitude) flow in a particular direction in the medium.

[0279] In isolation (e.g., when not installed in a flow configuration that may bias flow in a particular direction), an isotropic porous wall is configured to allow flow in any direction therethrough. Thus, the local direction of flow at any point within the isotropic porous wall is determined by the local pressure gradient and the relative flow resistances provided by different routes through the network of flow paths defined by the isotropic porous wall.

[0280] In the exemplary flow configuration 100, fluid is forced to flow over (i.e., through) each porous wall 110, 120 by a pressure differential between the fluid in the inlet chamber 102 and the fluid in the respective outlet chambers 130, 140. The pressure differential acts to drive flow through the porous walls 110, 120, which may be generally along the thickness direction 112. This is because the resistance offered by any particular path through a porous medium is a function of the path's length, and the thickness direction 112 provides the shortest distance between the inlet and outlet sides of the porous wall. However, at each point along an isotropic porous wall, the particular local route taken through the network of flow channels may depend on local variations in porosity, resulting in local routes through the isotropic porous wall that meander, as shown by exemplary route 113.

[0281] 1c, in a second example, the first porous wall 110 and the second porous wall 120 each have an anisotropic porous configuration provided by a plurality of angled channels 114 extending from an inlet side through the respective walls to an outlet side. For illustrative purposes, only the first porous wall 110 is shown, but the following description applies equally to both porous walls 110, 120. Each of the channels 114 is elongated along a path that is angled with respect to both the longitudinal direction A and the thickness direction 112 of the respective porous wall, such that flow along the channel from the inlet chamber 102 to the respective outlet chamber has a longitudinal component.

[0282] As used herein, the phrase "longitudinal component" refers to a component of a path that is along (i.e., parallel to and of the same sign / direction as) the longitudinal direction A. In the example described herein, the longitudinal direction extends from the proximal end to the distal end of the flow configuration; therefore, the definition of a path along which something is elongated as having a longitudinal component requires that the path have a positive longitudinal component in the proximal-to-distal direction. As shown in FIG. 1b, in this example, the longitudinal direction A corresponds to a vertically upward direction, and each of the porous walls 110, 120 is inclined so that flow passing therethrough from the inlet chamber 102 to the respective outlet chambers 130, 140 flows along a path 115 having an upward component.

[0283] The expression "channel" as used herein relates to an open path for flow that is free from obstructions and is bounded by the boundary walls of the channel.

[0284] 1d, in a third example, the first porous wall 110 and the second porous wall 120 each have a discontinuous porous structure, whereby each porous wall comprises a body 116 and a plurality of porous regions 118 extending from an inlet side of the body (adjacent the inlet chamber) through the body to an outlet side of the body (adjacent the respective outlet chamber). For illustrative purposes, only the first porous wall 110 is shown, but the following description applies equally to both porous walls 110, 120. Similarly, flow configurations may be implemented in which only one of the porous walls has a discontinuous porous structure as described herein.

[0285] The body 116 is elongate along a longitudinal direction A and defines the overall profile of the porous walls 110, 120 having a thickness direction 112 from the inlet side to the outlet side.

[0286] A plurality of porous regions 118 extend through the body 116 at discrete locations to allow fluid to flow from the inlet chamber 102 to the respective outlet chambers 130, 140. Each porous region 118 defines a respective network of flow paths through the body (resulting in multiple discrete networks of flow paths through the body). In this example, each porous region 118 is elongated along a path 119 through the body that has a longitudinal component (sometimes referred to herein as a "graded discontinuous porous structure"). However, it is also contemplated that a porous region may extend along a path through the body that does not have a longitudinal component (e.g., perpendicular to the longitudinal direction).

[0287] Each porous region 118 is defined by a porous medium (i.e., a medium having open porosity). As in the example of Figure 1c, the local route through the network of flow channels provided by a particular porous region 118 may be tortuous and may depend on variations in local porosity and the relative resistance to flow provided by different routes. An exemplary tortuous route is indicated by arrow 119.

[0288] Any of the flow configurations described above is suitable for implementation in an electrolytic cell, with each porous wall corresponding to (e.g., providing) a respective electrode of the electrolytic cell. The present disclosure contemplates that two porous walls of the same flow configuration may have any combination of the three configurations described above with respect to FIGS. 1b, 1c, and 1d. At least one of the porous walls may have a discontinuous porous structure (e.g., according to the example of FIG. 1d). At least one of the porous walls may have an anisotropic porous structure defined by a plurality of inclined channels (e.g., according to the example of FIG. 1c). At least one of the porous walls may have an isotropic porous wall (e.g., according to the example of FIG. 1b). When such flow configurations are implemented in an electrolytic cell, fluid reaction products such as hydrogen or oxygen may be produced at each electrode defined by the porous walls.

[0289] By separating the inlet chamber 102 and the outlet chambers 130, 140 by respective porous walls 110, 120 as disclosed herein, each porous wall serves (e.g., is configured) to inhibit return flow of the respective fluid reaction products through the respective porous wall toward the inlet chamber without relying on an ion exchange membrane. Such return flow is sometimes referred to herein as backflow. The porous walls are porous to allow fluid flow therethrough and to allow ion exchange in either direction to enable each half-reaction of the electrolysis. Thus, flow configurations as disclosed herein can be implemented in electrolytic cells without the use of ion exchange membranes, such as polymer electrolyte membranes (PEMs), between the respective electrodes.

[0290] By allowing fluid flow (e.g., of electrolyte solution) between the inlet chamber 102 and the outlet chambers 130, 140, each porous wall 110, 120 fluidly connects the inlet and outlet chambers to one another, thereby linking the pressures within the respective chambers. Compared to configurations that prevent fluid communication between such chambers, this can prevent excessive pressure differentials from being established across such walls / electrodes / membranes that could deform or otherwise damage the integrity of any intervening walls / electrodes / membranes and the associated electrolytic cell. The risk of such damage can be more pronounced during operation at high pressures, such as those for operation at supercritical conditions (i.e., temperatures and pressures above the supercritical points of the respective fluids). Therefore, providing a porous wall to separate each outlet chamber from the inlet chamber can protect or improve the structural integrity of the electrolytic cell, particularly for high-pressure operation.

[0291] By providing porous walls 110, 120 between the inlet chamber 102 and each outlet chamber 130, 140, a flow restriction is provided for flow therethrough, such that fluid flow through the wall is related to the pressure drop established across the porous wall. The pressure drop and the fluid flow rate through the component are related to each other and also depend on the properties of the component (e.g., its flow coefficient K, which may be considered constant). V ) and the fluid properties (e.g., specific gravity SG). The pressure drop across the porous wall inhibits backflow of each fluid reaction product through the porous wall towards the inlet chamber because such flow opposes the pressure gradient across the wall.

[0292] When the flow configuration comprises one or more porous walls according to the second and third examples (described above with respect to Figures 1c and 1d, respectively), an additional mechanism for suppressing backflow may be provided.

[0293] In particular, in such a configuration, there may be a predominant buoyancy-driven flow toward the or each outlet chamber. The buoyancy-driven flow may be biased to flow upward due to the relatively lower density of the fluid reaction product. Thus, when the inclined channel 114 (second example) or porous region 117 (third example) is elongated along a path having an upward component, the return flow therethrough may oppose the direction of the predominant buoyancy-driven flow and therefore be suppressed.

[0294] As an example, in an electrolytic reaction involving an aqueous electrolyte solution, the fluid reaction products (oxygen and hydrogel) have a lower density than water (or any suitable electrolyte solution), and as a result, buoyancy forces on those fluid reaction products tend to drive those fluid reaction products upward. When the respective reactions take place within the inclined channels 114 of a porous wall having inclined channels (second example in FIG. 1c) or within the porous regions 117 of a porous wall having a gradient discontinuous porous structure (third example in FIG. 1d), or when reaction products are provided to such locations in other manners, buoyancy forces acting due to the lower density of the respective fluid reaction products can drive flow upward, thereby along the respective inclined channels 114 or porous regions 117, toward the respective outlet chambers.

[0295] In a third example porous wall, as shown in Figure 1d, there are no inclined channels through the porous wall. To allow fluid to flow through the body, there are multiple discrete porous regions, each extending along a path having a longitudinal component.

[0296] By providing flow configuration 100 with porous walls according to the third example of FIG. 1d, (i) flow rate and (ii) flow effects related to backflow may depend on the properties of each of the porous regions. First, the flow rate through the or each porous wall may be determined at least in part by properties of the porous region 117, such as porosity, cross-sectional area or diameter, and length of the porous region, other than the orientation of the path along which the porous region extends. Such properties may be referred to herein as properties of the porous region 117 related to flow rate.

[0297] Second, by providing the porous region 117 along a path having a longitudinal component (e.g., a vertical component in use) and thus extending at an angle relative to the longitudinal direction, routes through each respective network of flow channels are effectively constrained along paths having a longitudinal component (e.g., within the boundaries of the porous region oriented at an angle relative to the longitudinal direction). The porous region 117 can be configured so that most, and optionally all (every) route through the network of flow channels has a longitudinal component (e.g., a route may have a net positive longitudinal component corresponding to the longitudinal direction of the respective porous wall, regardless of whether the route has a serpentine path through the porous region 117 with localized upward and / or downward components). Thus, without having to specifically configure each flow channel of the porous region to provide such a longitudinal component, this can nevertheless be achieved for most, or optionally all (every) route through the porous region. Therefore, return flow through the porous region is suppressed because it opposes the direction of the prevailing buoyancy-driven flow. For example, each porous region 117 may be configured such that, with respect to longitudinal position, the outlet end of the porous region 117 is longitudinally spaced apart from the inlet end of the porous region 117, and the longitudinal extension ranges of both ends do not overlap.

[0298] The flow effect of suppressing backflow due to buoyancy effects is related to the characteristics of the path along which the porous region extends, for example the angle of the path relative to the longitudinal direction.

[0299] Thus, in designing and configuring a flow configuration having one or more porous walls according to the third example of FIG. 1d, the above-described flow effects can be separately specified and controlled by reference to the characteristics of each of the porous regions 117. For example, one or more characteristics of the porous regions 117 related to flow rate (e.g., the porosity, cross-sectional area or diameter, and / or length of the porous regions) may be selected or configured to target a performance characteristic related to flow rate. Additionally, and separately, characteristics of the path along which the porous regions 117 extend (e.g., the inclination angle of the path) may be selected or configured to target a performance characteristic related to backflow (e.g., to control or inhibit crossover of reaction products between outlet chambers). The length of the porous regions may depend on the inclination angle, and thus there may be some correlation between flow rate-related and buoyancy-related flow effects.

[0300] As an example, flow effects related to the flow rate through a porous wall may include the resistance to flow presented by the porous wall, which may otherwise be expressed as its efficiency in allowing fluid flow (e.g., the flow coefficient K of either the porous wall as a whole, the porous area as a whole, or an individual porous area). V Resistance to fluid flow / efficiency (e.g., flow coefficient K V) relates the flow rate to the pressure drop. In various embodiments of the electrolytic cell, the pressure drop can be fixed and the flow rate can be variable, or the flow rate can be fixed (e.g., the total inlet flow rate) and the pressure drop can be variable. Another exemplary flow effect related to flow rate is the balance of flow rates through the first and second porous walls. For example, when one of the porous walls offers a lower flow resistance than the other, the flow can be biased through the respective wall. Thus, as discussed herein, properties related to the flow rate through the porous walls can be selected to control (e.g., target or mitigate) the flow bias. When a flow configuration such as that described above is implemented in an electrolytic cell with porous walls corresponding to (e.g., providing) the electrodes of the electrolytic cell, a flow bias toward one porous wall or another can affect diffusion and / or species crossover effects within the electrolytic cell, as discussed further below.

[0301] The porous medium of the porous regions 117 may be formed or provided without control over the directional orientation of the porous medium, and thus the porous medium itself may have a structure or porosity that does not vary by more than an order of magnitude according to directional measurements. Within the boundaries of each porous region 117, the porous medium may or may not be substantially isotropically arranged. In any case, it is contemplated that the porous medium of each porous region 117 itself may not be provided for the purpose of directional bias per se; instead, it is contemplated that the profile or path of the porous region itself may provide anisotropy to the porous walls, for example, to provide any buoyancy-related effects to suppress backflow.

[0302] Flow effects and example properties of porous region 117 and body 116 are further discussed below in connection with simulation results.

[0303] The third exemplary porous wall 110 of FIG. 1d is shown as having a porous region 117 extending through the entire extent of the body along the thickness direction, but in an alternative embodiment, the porous region 117 may have an extent along the thickness direction that is less than the thickness of the body.

[0304] In an alternative of any of the above examples, the flow configuration as described above need not be axially symmetric. For example, the flow configuration may comprise a linear duct partitioned by the porous walls into adjacent inlet and outlet chambers (i.e., a central inlet chamber and two outer outlet chambers).

[0305] The exemplary flow configuration of FIG. 1a schematically shows first and second outlets 132 and 142 at the distal ends of the first and second outlet chambers, but it will be appreciated that the outlets from the outlet chambers may be provided at any suitable location. Nevertheless, the outlets may generally be longitudinally separated at the portions of the outlet chambers that receive the flow through the respective porous walls.

[0306] The electrolytic cell can comprise a flow configuration 100 as described above with reference to FIG. 1a, where one or both of the porous walls 110, 120 have the configuration as described above with reference to FIGS. 1b - 1d or the configuration as described below with reference to any of FIGS. 2a - 2c. In such an electrolytic cell, each of the porous walls 110, 120 can provide the respective electrodes of the electrolytic cell, i.e., the anode or the cathode. The configuration of the electrolytic cell comprising the exemplary flow configuration 100 substantially corresponds to the configuration of the flow configuration as described above, and thus FIG. 1a is considered to show the configuration of the electrolytic cell 100.

[0307] The above description is mainly related to the flow effects in the flow configuration, but the following further description of the electrolytic cell 100 of FIG. 1a is given in relation to the function and configuration of the porous walls 110, 120 as electrodes, particularly with reference to any electrolytic catalyst regions and / or passive regions of the electrodes (described with reference to FIGS. 2a - 2c).

[0308] It will be appreciated that the electrolytic cell 100 may be provided with further components in addition to those shown in FIG. 1a, such as, for example, electrical connections to the electrodes (also known as electrical feedthroughs) provided by the porous walls.

[0309] Each of the porous walls 110, 120 may have an electrocatalytic region containing an electrocatalyst for each half-reaction of the electrolysis. In use, the fluid reaction products of each of the electrolytic reactions are produced in the electrocatalytic region. For example, in the electrolysis of an aqueous electrolyte to produce hydrogen and oxygen, hydrogen is produced in the electrocatalytic region of the cathode, and oxygen is produced in the electrocatalytic region of the anode. A wide variety of materials are suitable as electrocatalysts, and the particular choice of electrocatalyst may depend on the electrolyte selected. Exemplary electrocatalysts and electrolytes are discussed elsewhere herein.

[0310] The following disclosure relates to exemplary configurations of porous walls 110, 120 as described above to provide respective electrocatalytic and / or passive regions. The following disclosure refers to Figures 1b-1d and 2a-2c, each showing a first porous wall 110. However, it will be appreciated that the following disclosure is equally applicable to the second porous wall 120.

[0311] When the porous wall 110 (either as an anode or cathode) has an isotropic porous configuration according to the first example of FIG. 1b, the electrocatalyst region can be defined by the porous medium and can effectively correspond to the entire porous wall, excluding any passivating coating (discussed below). For example, the porous medium can have a material composition that includes (e.g., consists essentially of, consists of, or is) an electrocatalyst suitable for each half-reaction of the electrolysis. The porous medium can be formed from a material that includes the electrocatalyst. In other aspects, the porous medium can be defined by a matrix having a coating, the matrix having a first material composition and defining a network of flow channels through the porous wall, and the coating provided on the matrix having a second composition that includes (e.g., consists essentially of, consists of, or is) an electrocatalyst for each half-reaction of the electrolysis. The coating may be provided on surfaces of the matrix that define a network of flow paths through the porous medium (e.g., including interior surfaces within the porous walls), and may be provided at a coating thickness that maintains porosity through the porous walls to permit fluid flow therethrough ("porosity" refers to open porosity as described above).

[0312] 2a illustrates a fourth exemplary configuration of the porous wall, corresponding to the first example of FIG. 1b, except that passive regions 202 are provided on the inlet side of the porous wall adjacent the inlet chamber 102. As discussed elsewhere herein, the passive regions are configured to suppress the respective half-reactions of the electrolysis. The passive regions can suppress the respective half-reactions of the electrolysis by being less electrocatalytically active than the electrocatalytic regions for the respective half-reactions of the electrolysis, as discussed elsewhere herein.

[0313] Providing a passive region (which may be formed by a passivation coating) defining the inlet side of the porous wall has the effect of inhibiting the respective electrolytic half-reactions from occurring within the inlet chamber 102. Thus, the respective electrolytic half-reactions may occur primarily when the electrolyte solution passes through the passive region and reaches the electrocatalytic region, with the respective fluid reaction products being produced downstream of the passive region relative to the direction of flow through the respective porous wall. As noted above, the porous walls disclosed herein have the effect of inhibiting backflow of the fluid reaction products, thereby inhibiting the fluid reaction products from flowing upstream back into the inlet chamber 102.

[0314] When the porous wall 110 (either as an anode or cathode) has an anisotropic porous configuration according to the second example of Figure 1c, the electrocatalytic regions may be defined by the material of the porous wall itself or by (for example) an electrocatalytic coating on at least the interior walls of the channels 114. For example, the porous wall 110 may be formed by providing a body having a first material composition and forming the channels 114 to extend through the body. When the first material composition includes an electrocatalyst suitable for each half-reaction of the electrolysis, the body defines the electrocatalytic regions of the porous wall.

[0315] Alternatively, the porous wall 110 may be formed by providing a body, forming channels 114 extending therethrough, and coating the surface of the body, including at least the interior walls of the channels 114, with a coating including an electrocatalyst for each half-reaction of the electrolysis, thereby defining each electrocatalytic region of the porous wall. The body may define the passive regions of the porous wall as discussed herein; for example, the body may include (e.g., consist of) a material that is not electrocatalytically active for each half-reaction of the electrolysis, or that is less electrocatalytically active than the electrocatalytic regions, such as a body such as stainless steel 316 or titanium (e.g., coated with an electrocatalytic coating including, for example, nickel or platinum).

[0316] FIG. 2b shows a fifth exemplary configuration of the porous wall corresponding to the second example of FIG. 1b, except that a passive area 202 is provided on the inlet side of the porous wall adjacent to the inlet chamber 102.

[0317] For example, the passive region may be provided as a passivation coating on the inlet side of the porous wall. The passivation coating may be provided when the body has a first material composition containing the electrocatalyst (so that the electrocatalyst region corresponds to the extension of the body) or when the body is provided with a coating containing the electrocatalyst. The passivation coating may be provided before or after forming the channel 114. Whether it is applied before or after the channel formation may be selected depending on the application manner. For example, when using an immersion-based technique (e.g., dip coating), the passivation coating may be applied before the formation of the channel 114 to prevent the passivation coating from flowing into the channel. However, for other techniques, such as CVD (chemical vapor deposition), the diminishing effect associated with the deposition of the passivation coating may be such that only a limited amount of the passivation coating penetrates into the walls of the preformed channel, so that application after the channel formation may be selected.

[0318] When the porous wall 110 (either as an anode or cathode) has a discontinuous porous structure according to the third example of FIG. 1d, the electrocatalytic region can be defined by (i) the porous region 117 (e.g., only) or (ii) the body 116 and the porous region 117. In a first alternative, the body may have a first material composition and define the passive region of the porous wall (e.g., may comprise (e.g., consist essentially of, consist of, or be) stainless steel 316 or titanium), while the porous region 117 may have a second material composition containing an electrocatalyst for each half-reaction of the electrolysis (e.g., nickel or platinum; further suitable electrocatalysts are described elsewhere herein), thereby defining the electrocatalytic region of the porous wall. Exemplary methods for forming the porous region 117 using different material compositions are described below with reference to FIG. 3a.

[0319] In a second alternative, as described above, the body may have a first material composition containing an electrocatalyst for each half-reaction of the electrolysis, and the porous regions may be integrally formed with the body and may have the same first material composition, or may have a second material composition also containing an electrocatalyst for each half-reaction of the electrolysis. When the porous regions are integrally formed with the body and have the same first material composition, each porous region 117 surrounds the porous region 117 and interfaces with the body at a respective boundary defined by the change in porosity between the body and the porous region. An exemplary method for integrally forming the body 116 and porous region 117 is described below with reference to FIG. 5.

[0320] 2c shows a sixth exemplary configuration of a porous wall corresponding to the third example of FIG. 1c, except that a passive region 202 is provided on the inlet side of the porous wall adjacent the inlet chamber 102. The passive region 202 may be provided as a passivation coating as described elsewhere herein, and may be applied before or after the formation of the porous region, as described above. As mentioned above, exemplary methods for forming a porous wall having a discontinuous porous structure are described below with reference to FIGS. 3a and 5, and such methods illustrate the formation of a passive region (which may include a passivation coating).

[0321] To further illustrate the flow paths and electrolysis reaction locations within an electrolytic cell 100 having one or more porous walls according to the flow configuration of Figure 1a and any of the first through sixth examples of Figures 1b-2c, an example use will now be described. The example use will be described with reference to electrolysis with an electrolyte liquid that is a water-based (aqueous) electrolyte liquid (e.g., electrolyte solution) at supercritical conditions for flow through each electrode, such as a pressure of 22.5 MPa and an inlet temperature of 375°C.

[0322] At supercritical conditions, fluids behave as if they do not have distinct liquid and gas phases. Supercritical electrolytes can be advantageous for use in electrolysis compared to subcritical electrolytes. In particular, supercritical fluids are completely miscible with each other, resulting in a mixture of fluids forming a single phase with no interface or surface tension between them. Therefore, when reaction products are supercritical rather than gaseous when they are produced (e.g., because they have a lower critical temperature and pressure than the electrolyte, or because the temperature and pressure are otherwise higher than their respective critical points), they are completely miscible with the electrolyte. Therefore, reaction product bubbles do not accumulate on the surfaces of the electrodes. Such accumulation could otherwise inhibit the reaction by preventing local interaction between the electrolyte and the electrodes.

[0323] Furthermore, it is known that the conductivity of electrolyte liquids tends to be higher at elevated temperatures and pressures (see, for example, the paper "High Pressure Electrolyte Conductivity of the Homogeneous, Fluid Water-Sodium Hydroxide System to 400°C and 3000 bar," A. Eberz and E.U. Franck, Ber. Bunsenges. Phys. Chem. 99, 1091-1103 (1995) No. 9, especially Table 2). Without wishing to be bound by theory, it is believed that the dissociation constant and conductivity of water increase with increasing temperature and pressure. Furthermore, the conductivity of an electrolyte or electrolyte liquid (e.g., an electrolyte solution) is a function of pressure and temperature, and it is observed that conductivity increases as the pressure and temperature increase toward the critical point. Within the supercritical range (i.e., within the range of pressure and temperature conditions where the temperature is at least the critical temperature of the fluid and the pressure is at least the critical pressure of the fluid), conductivity can decrease with increasing temperature at constant pressure. However, conductivity can increase within the supercritical range as pressure is increased. Thus, the concentration of electrolyte in the electrolyte solution can be reduced by operating at relatively high temperatures and pressures. The supercritical range is an example of a relatively high pressure and temperature condition, and it is believed that operation within the supercritical range can provide a relatively higher conductivity of the electrolyte solution compared to operation within the subcritical range, which is at temperatures and pressures significantly below the critical temperature and pressure. Operation in conditions where the electrolyte solution has a higher conductivity can reduce the ohmic losses associated with the electrolyte while still providing adequate conductivity, or alternatively, allow the use of a different electrolyte associated with reduced ohmic losses.

[0324] By way of example only, a suitable electrolyte solution for use with the exemplary electrolytic cell 100 described above is an aqueous electrolyte solution containing NaOH as the electrolyte (further suitable electrolyte solutions are disclosed elsewhere herein). As noted above, the conductivity of electrolyte solutions tends to increase with temperature and pressure.

[0325] To illustrate the above trend of increasing conductivity with pressure and temperature, reference may be made to the above-referenced paper by Eberz and Franck, which reports that at 0.1 MPa and 25°C, an electrolyte composed of NaOH having a concentration of 17 wt. % exhibits a conductivity of 0.4 Scm -1 while at 30 MPa and 400°C the electrolyte exhibits a conductivity of 1.3 Scm -1 For a 0.5M NaOH solution, the conductivity at 22.5 MPa and 375°C is approximately 150-200 mScm -1 while at 0.1 MPa and 25°C the conductivity is about 100 mScm -1 It is estimated that this may be the case.

[0326] As an example of an electrolyte solution suitable for use with the exemplary electrolytic cell 100, the electrolyte solution may include an aqueous solution containing 0.5M NaOH.

[0327] In this example, the first porous wall 110 is configured as a cathode (for hydrogen production) and the second porous wall is configured as an anode (for oxygen production) (depending on the respective electrical configurations of the electrolyzers).

[0328] As described above with respect to the general flow path through the flow configuration 100 of FIG. 1, when electrolyte solution is provided to the inlet chamber 102 via the inlet 101, branch flows are established through the respective porous walls (electrodes) 110, 120 to the respective outlet chambers 130, 140.

[0329] As the flow passes through the electrocatalytic region of each porous wall, the respective half-reactions of the electrolysis are carried out. In particular, the electrolyte undergoes a reduction reaction as it passes through the electrocatalytic region of the first porous wall 110 (cathode) to produce a fluid reaction product, which in this example is supercritical hydrogen, and the electrolyte undergoes an oxidation reaction in the second porous wall 120 (anode) to produce a fluid reaction product, which in this example is supercritical oxygen. Ions are transferred between the anode and cathode, for example, by electromotive forces. In this particular example, hydroxide ions (OH - ) is transferred through the electrolyte to the anode (along with the transfer of electrons to the anode) to produce a fluid reaction product (oxygen) at the anode.

[0330] In this example, the pressure and temperature conditions of the electrolytic cell are controlled so that both the electrolyte liquid and each of the fluid reaction products are in a supercritical state at the porous walls. Thus, the fluid reaction products are believed to be fully miscible with the electrolyte liquid within the porous walls without forming an interface (e.g., a bubble interface) between them, as described above.

[0331] When the electrocatalytic regions of each porous wall do not define an inlet side of the respective porous wall, the respective half-reactions of the electrolysis do not tend to take place on the inlet side of the porous wall, and therefore the respective fluid reaction products do not tend to be produced in the inlet chamber.

[0332] For an isotropic porous wall, when a passive region is present, as described above with respect to the fourth example of Figure 2a, the electrocatalytic region may not define the inlet side of the porous wall. For an anisotropic porous wall with inclined channels 114, as in the second and fifth examples of Figures 1c and 2b, respectively, when the body of the porous wall defines a passive region of the porous wall by an electrocatalytic region defined in the walls of the channels 114 (e.g., by a coating containing an electrocatalyst), the electrocatalytic region may not define the inlet side of the porous wall. In other aspects, an anisotropic porous wall may have a passive region that defines the inlet side, as in the fifth example of Figure 2b. Similarly, for porous walls having a discontinuous porous structure as discussed herein, the electrocatalytic region may not define the inlet side of the porous wall by the electrocatalytic region being limited to the porous region 117 and body 116 that define the passive region of the porous wall (as in the third example of FIG. 1d) and / or by having a passive region that defines the inlet side as in the sixth example of FIG. 2c.

[0333] Thus, when the porous wall is according to any of the second through sixth examples of Figures 1c-2c, the respective half-reactions of the electrolysis do not tend to occur in the inlet chamber, but instead occur as the flow passes through the porous wall itself, and in particular, the electrocatalytic region. The location of each half-reaction of the electrolysis is therefore downstream of the inlet chamber with respect to the direction of the branched flow of fluid from the inlet chamber to the outlet chamber, as described above.

[0334] For each of the exemplary configurations of porous walls described herein, backflow of fluid reaction products generated within the porous walls is suppressed by opposing pressure gradients acting through the walls. This effect can become stronger as the pressure differential acting across the respective porous walls increases. The fluid reaction products are effectively entrained in a pressure-driven flow through the respective porous walls, thereby limiting or reducing migration or diffusion of the respective fluid reaction products in the reverse direction.

[0335] When the porous wall has an anisotropic configuration according to the second, third, fifth, and sixth examples (i.e., has inclined channels 114 or has a graded, discontinuous porous structure with porous regions 117), the flow paths through the porous wall (e.g., most or all of them) can be effectively constrained to have a longitudinal component, which corresponds to the vertically upward component in this example. Therefore, buoyancy forces are believed to influence the flow as described above. The fluid reaction products each have a lower density than the electrolyte liquid and therefore tend to establish a buoyancy-driven flow through their respective porous walls and outlet chambers, causing the flow to preferentially flow upward. Backflow of the fluid reaction products is suppressed by buoyancy effects. This is because flow along the reverse direction toward the inlet chamber requires the fluid reaction products to move against the dominant buoyancy-driven flow in order to flow downward toward the inlet chamber.

[0336] At the supercritical conditions mentioned above (22.5 MPa and 375°C), the thermoneutral voltage for electrolysis is approximately 1.3 V, which corresponds to 35.62 kWh per kg of hydrogen reaction product produced. This is 110% of the higher heating value of hydrogen (39.4 kWh / kg) and 93.5% of the lower heating value of hydrogen (33.3 kWh), and therefore represents efficient electrolysis. To sustain the electrolysis reaction under these conditions, the ohmic losses in the electrolyzer should be less than 0.120 V. In this example, the ohmic losses in the electrolyzer (approximately 150 mScm) -1 The voltage drop (associated with ion exchange through an exemplary electrolyte solution of 0.5 M NaOH, which has a predicted conductivity of 0.1 V) is about 0.11 V when the electrode spacing is 1 mm, while ohmic losses associated with bubble formation at the electrodes are eliminated by operation at supercritical conditions. The electrode spacing may be less than 1 mm, e.g., 0.5 mm or between 0.5 mm and 1 mm. Suitable electrocatalysts may be determined by one of skill in the art and are discussed elsewhere herein; however, by way of example only, suitable electrocatalysts may include nickel or a nickel alloy in the anode (which may be the first electrode) and nickel, a nickel alloy, or platinum in the cathode (which may be the second electrode).

[0337] Ohmic losses are a function of electrolyte conductivity and electrode spacing. For example, if the electrodes are spaced 3 mm apart, the ohmic losses are 2000 mScm -1 Higher electrolyte conductivities such as 0.1% may be required.

[0338] While exemplary supercritical conditions are described above, conditions may vary. For example, supercritical operation of an electrolytic cell may correspond to operation such that the electrolyte pressure is between 22 MPa and 27 MPa at the porous wall for aqueous electrolyte solutions, and the electrolyte temperature is at least 374°C at the porous wall for aqueous electrolyte solutions, e.g., between 374°C and 550°C, or between 374°C and 400°C.

[0339] In general, it may be desirable to operate to achieve lower temperatures and pressures toward the critical point in the porous walls, thereby minimizing the energy resources required to pressurize and heat the electrolyte liquid. While ohmic losses may be lower at higher temperatures and pressures, it is believed that any efficiency benefits that would be obtained at elevated temperature and pressure conditions may be offset by the additional energy required to heat and / or pressurize the electrolyte liquid, unless such additional energy is available as excess energy (e.g., excess heat from a heating source that would otherwise be released without heat recovery).

[0340] While the above discussion has focused on examples in which each porous wall 110, 120 provides an electrocatalytic region for reaction with the electrolyte liquid as it passes through the respective porous wall for each half-reaction of the electrolysis, the present disclosure contemplates embodiments of the flow configuration 100 in the electrolytic cell in which the electrocatalytic regions of the electrodes and / or porous walls are provided only in the outlet chambers associated with the porous walls. For example, electrodes may be disposed in the outlet chambers and separate from the respective porous walls, or electrocatalytic regions may be disposed only on the outlet side of the respective porous walls to form electrodes. In such an arrangement, the electrolytic cell is configured such that each half-reaction of the electrolysis occurs within (e.g., only within) the outlet chambers. Such an arrangement may be particularly suitable for use in non-supercritical conditions in which the fluid reaction products of each electrolysis reaction are immiscible (e.g., immiscible) with the electrolyte liquid at the electrocatalytic region and / or as they pass through the respective porous walls. When subcritical conditions prevail at the electrodes, bubbles may form between the respective fluid reaction products and the electrolyte solution when each half-reaction of the electrolysis occurs at the inlet side or within a flow path through the porous wall. The bubbles may have adverse flow effects; for example, each bubble may block a portion of the surface of the electrocatalytic region of each electrode (e.g., the porous wall), thereby inhibiting the ongoing reaction. Furthermore, the bubbles may block the flow path through the porous wall, thereby inhibiting both the ongoing reaction and the flow through the porous wall.

[0341] However, when the electrocatalytic regions of the or each porous wall of an electrode are provided within the outlet chamber as mentioned above, such effects related to interactions between gas bubbles and the porous wall can be avoided. In such embodiments, the separation between the electrocatalytic regions of the or each electrode can be relatively large compared to embodiments in which the or each porous wall provides a respective electrocatalytic region within the thickness of the porous wall (e.g., defines a flow path through the porous wall). This can increase ohmic losses.

[0342] The inventors have found that by suppressing backflow of fluid reaction products, for example by any of the mechanisms described above, the electrodes (e.g. porous walls) can be positioned with a relatively small separating gap between them (and without the use of a membrane), thereby reducing ohmic losses within the electrolytic cell.

[0343] In particular, by suppressing backflow, flow through the porous walls as described herein can be substantially unidirectional, even when the area of ​​the porous wall is relatively large for a given amount of flow (i.e., when the flow rate per unit area through the porous wall is relatively low) compared to previously considered configurations. In previously considered configurations, flow-through electrodes can be provided to span long ducts, resulting in either a relatively low electrode area relative to the flow rate or a relatively high flow rate per unit area through the flow-through electrodes. It is believed that providing a relatively high flow rate through the flow-through electrodes in previously considered configurations can prevent backflow primarily due to flow inertia.

[0344] For a given flow rate of electrolyte liquid, if the area of ​​the electrode is increased relative to such previously considered configurations, such inertial effects may be reduced and there may be a risk of local flow reversal that may allow mixing of reaction products. However, by providing a porous wall as disclosed herein, the flow rate per unit area can remain relatively low for a given reaction area of ​​the electrode (or, conversely, the reaction area can be relatively large for a given flow rate), while still relying on the porous wall as described herein to prevent flow reversal.

[0345] Thus, the inventors have discovered that it is possible to provide an electrolytic cell configuration in which the porous walls have a relatively large area for a given flow rate. As a result, the electrodes can have a relatively larger flow-through area for a given flow rate of electrolyte solution to the electrolytic cell and / or of reaction products produced by the electrolytic cell, allowing a relatively larger surface area for carrying out electrolytic reactions, which may enable higher reaction rates for a given electrolyte solution flow rate. These advantages apply equally to all exemplary configurations herein. The expression "flow-through area" as used herein with reference to a porous wall (electrode) is intended to refer to the area of ​​a substantially continuous surface extending across each boundary of the electrode's porous wall (e.g., the inlet side of the porous wall), rather than the total surface area of ​​the electrolyte interface defined by the porous medium (e.g., the surface defining a tortuous path through the porous medium within the electrocatalytic region of the porous wall).

[0346] As a result, the size of the electrodes can be relatively large compared to the cross-sectional area defined by the inlet chamber and / or the separation gap, and the separation gap between the electrodes can be relatively elongated. For example, the first porous wall and the second porous wall can face each other along a coextensive extension along which there is an average shortest separation distance between opposing ion exchange surfaces of the electrodes for ion exchange. The ratio of the coextensive extension (i.e., the distance along the longitudinal axis A along which the electrodes face each other for ion exchange) to the average shortest separation distance can be at least 5, e.g., at least 20 or at least 50 (e.g., 5 to 200, 20 to 200, 50 to 150, etc.).

[0347] In the particular example of electrolytic cell 100 of FIG. 1a, the electrodes have an equal extension range of 100 mm, while the average minimum separation distance is about 0.7 mm, resulting in a ratio of about 140.

[0348] 3a is a flow diagram of a method for manufacturing a porous wall for an electrolytic cell having a discontinuous porous structure, such as a porous wall according to the third example of FIG. 1d or according to the sixth example of FIG. 2c. The porous wall comprises a body and a plurality of porous regions. The method will be described by way of example with reference to the porous wall of the sixth example of FIG. 2c (using the reference numerals associated with FIG. 2c).

[0349] A body 116 for the porous wall is provided at block 302. In this example, the body 116 has a material composition corresponding to the electrocatalytic region of the porous wall, although in variations the body may have a material composition corresponding to the passive region of the porous wall.

[0350] The body may have a shape and size corresponding to the shape of the porous wall to be manufactured. The body may be machined to match that shape and size. The dimensions of the porous wall may correspond to the exemplary dimensions provided for (either of) the inner and outer electrodes as specified in Table 2 below.

[0351] In this example, the body includes (e.g., consists of) nickel or a nickel alloy. In this particular example, the body consists of a nickel-chromium alloy (specifically, an Inconel® alloy, Inconel® 600).

[0352] In example variations in which the body has a material composition corresponding to the passive region of the porous wall, the material composition of the body may be such that the body is less electrocatalytically active than the porous region, as defined herein, and thus the body, when fabricated, may form the passive region of the porous wall. For example, the body may have a material including (e.g., consisting essentially of, consisting of, or is) stainless steel 316 or titanium.

[0353] In any case, the body has a material composition for conducting electrical current such that the body is configured to conduct electrical current between the electrocatalytic regions of the porous wall (as described below) and electrical connections in the electrolytic cell, thereby serving as an electrode (e.g., an anode or cathode) in the electrolytic cell.

[0354] Optionally, at block 304, a passivating coating (e.g., a dielectric coating) is applied to one side of the body to define the passive regions 202 of the porous wall. In this example, the body material composition is electrocatalytic, and therefore the passivating coating is applied. In an example variation in which the body has a material composition corresponding to the passive regions of the porous wall, the porous regions corresponding to the body and the passive regions corresponding to the passivating coating may be considered to be first and second passive regions, each less active as an electrocatalyst than the porous regions according to any definition herein.

[0355] The passivation coating may be applied by any suitable process, for example, a sputtering process such as magnetron sputtering, a chemical vapor deposition (CVD) process, or an immersion process. One side of the body may be masked to prevent coating with the passivation coating (e.g., the outlet side of the body). Optionally, the passivation coating may be applied to both sides of the body (i.e., both the inlet and outlet sides without either side being masked).

[0356] At block 306, open regions extending through the body are formed at discrete locations to provide the body with an anisotropic porous structure. The open regions correspond to the porous regions 117 formed in body 116. Thus, the open regions are formed elongately along paths through the body having a longitudinal component, as described above with respect to porous regions 117. The open regions are formed by removing material from the body, for example, using a laser drilling process.

[0357] The open regions may be formed with an average cross-sectional diameter along their length of 25 to 150 μm, e.g., 50 to 250 μm, 50 to 150 μm, 70 to 150 μm, or about 120 μm, and may each have a generally circular cross-section perpendicular to the path along which they each extend.

[0358] The open areas may be formed to have a midpoint diameter of 25 to 250 μm, for example, 25 to 100 μm, 25 to 80 μm, or 25 to 50 μm.

[0359] The open area may be formed to have an entrance diameter of 25 to 250 μm, for example, 50 to 250 μm, 50 to 150 μm, 70 to 150 μm, or about 120 μm.

[0360] The open area may be formed to have an exit diameter of 25 to 250 μm, for example, 50 to 250 μm, 50 to 150 μm, 70 to 150 μm, or about 120 μm.

[0361] Open area: 10,000 to 250,000 μm 2 , for example, 15,000 to 250,000 μm 2 , 15,000~150,000μm 2 , 20,000~150,000μm 2 , 50,000~150,000μm 2 , or approximately 100,000 μm 2 The average cross-sectional area may be determined as the volume of the open region divided by the extent of the open region along the thickness of the body.

[0362] An example of a suitable laser drilling device is the "Lasertec 50 Powerdrill" available from DMG Mori Seiki Co., Ltd., Japan, or a high-power ultrashort pulse laser available from Amphos GmbH, Germany (e.g., the "Amphos 2302" or "Amphos 3000" series lasers). Further examples of suitable laser drilling devices are, for example, the series of machines available from IPG Photonics, USA, referred to as QCW fiber lasers (quasi-continuous wave lasers) that can operate in both pulsed and continuous wave modes to generate pulses of 4 to 200 joules at various pulse frequencies, e.g., from 100 Hz to 5 kHz.

[0363] A suitable laser drilling process may be ultrashort pulse laser drilling (also known as laser micromachining), where the ultrashort laser pulses are in the picosecond or femtosecond range, such as 10 ps, ​​or 0.1 ps to 10 ps. Such machining processes are discussed in the reference Aizawa Tatsuhiko and Inohara Tadahiko (2019), "Pico- and Femtosecond Laser Micromachining for Surface Texturing," also available at https: / / www.intechopen.com / books / micromachining / pico-and-femtosecond-laser-micromachining-for-surface-texturing.

[0364] At block 308, the method includes depositing an electrocatalyst composition on the body such that the composition flows into the open area.

[0365] The electrocatalyst composition is a composition comprising (e.g., consisting essentially of, consisting of, or is) an electrocatalyst for each half-reaction of the electrolysis. For example, the electrocatalyst composition may comprise (e.g., may consist essentially of, or may consist of) a mixture of an electrocatalyst for each half-reaction of the electrolysis and a liquid. The electrocatalyst composition may comprise (e.g., may be, may consist essentially of, or may consist of) a slurry containing an electrocatalyst for each half-reaction of the electrolysis and a liquid. The electrocatalyst composition may comprise (e.g., may be, may consist essentially of, or may consist of) a suspension of an electrocatalyst for each half-reaction of the electrolysis in a liquid. The electrocatalyst may be provided in the form of particulates. The suspension may be a colloidal suspension (e.g., of particulates in a liquid). For example, the electrocatalyst composition may comprise (e.g., may be, consist essentially of, or consist of) a sol (i.e., a solid-liquid colloidal suspension) containing the electrocatalyst for each half-reaction of the electrolysis, a conductive ink (i.e., a suspension of conductive electrocatalyst particles in a liquid), or a paste (i.e., a solid-liquid suspension with a solids content high enough that the suspension behaves as a solid in response to the application of low stress). The liquid, such as a solvent, can affect the viscosity of the electrocatalyst composition. In addition to the electrocatalyst and the liquid, the electrocatalyst composition may include a binder (e.g., a polymeric binder such as a resin binder) and / or one or more additives. Exemplary electrocatalyst compositions are discussed below and elsewhere herein.

[0366] The electrocatalyst composition may be applied to the body by any suitable method.

[0367] For example, the electrocatalyst composition can be deposited on a surface of the body and rubbed (e.g., spread) on the surface along a deposition direction parallel to the longitudinal direction of the body. The deposition direction (i.e., forward or backward along the longitudinal direction) can be selected to facilitate directing the electrocatalyst composition into the open region, which can vary depending on the side of the body to which the electrocatalyst composition is deposited. For example, if the open region is elongated along a path toward the side of the body corresponding to the outlet side of the porous wall, and the path is at an angle of 70° relative to the longitudinal direction of the body, the deposition direction would be forward along the longitudinal direction if the electrocatalyst composition is deposited on the side of the body corresponding to the inlet side of the porous wall, and would be backward along the longitudinal direction if the electrocatalyst composition is deposited on the side of the body corresponding to the outlet side of the porous wall.

[0368] The electrocatalyst composition may be rubbed (e.g., drawn) onto the surface by an applicator, which may be a flexible applicator having a shape corresponding to the shape of each side of the body. When the body is substantially flat, the applicator may have a substantially linear profile terminating in a linear applicator lip. When the body is substantially annular, the applicator may have a corresponding annular profile with a substantially circular lip. For annular bodies, the electrocatalyst composition may be applied from a radially outer or radially inner direction. An applicator for radially outer application may include a frustoconical applicator tapering inward toward the lip and configured to slide longitudinally over the body. An applicator for radially inner application may include a frustoconical applicator tapering outward toward the lip and configured to slide longitudinally through the body in a plunger action.

[0369] Applying a vacuum to one side of the body can assist in penetration of the electrocatalyst composition into the open areas on the opposite side of the body. For example, when the electrocatalyst composition is applied to the annular body from a radially outward direction, a vacuum can be applied to the interior of the body to draw the electrocatalyst composition into the open areas at the exterior of the body. Alternatively, when the electrocatalyst composition is applied to the annular body from a radially inward direction, a vacuum can be applied to the exterior of the body to draw the electrocatalyst composition into the open areas at the interior of the body.

[0370] Excess electrocatalyst composition can be removed by a scraper blade, which can have a configuration similar to the applicator, but differs by being relatively less flexible (e.g., having a higher bending stiffness) so that it is configured to remove excess electrocatalyst rather than bending and directing it into the open area.

[0371] FIG. 3b shows an exemplary applicator for a cylindrical porous wall 110 having a porous longitudinal extension 111. The applicator includes two opposing plungers 309, 309′ configured to be slidably and sealably inserted into opposite ends of the porous wall 110 and compress the electrocatalyst composition therebetween, thereby driving the electrocatalyst composition under pressure into the open area of ​​the porous wall 110 from radially inward (e.g., the outlet side for the first porous wall 110) to radially outward (e.g., the inlet side for the first porous wall 110). The applicator can be used for either porous wall to ensure that the electrocatalyst flows through and occupies the open area throughout the entire extension of the body along the thickness direction. One of the applicators 309, 309′ can be removed, and the other can be driven through the longitudinal extension of the porous wall 110 to remove excess electrocatalyst composition from the interior of the porous wall. 3b, at least one of the applicators 309, 309′ can have a conical end configured to mate with (e.g., abut) the opposing applicator. A predetermined amount of electrocatalyst composition can be dispensed into the porous wall such that the mating between the applicators corresponds to the application of sufficient relative motion to drive the electrocatalyst composition through each of the open areas of the porous wall 110.

[0372] Referring back to FIG. 3 a, at block 310, the method optionally includes a drying operation in which the electrocatalyst composition as applied to the body is dried to (e.g., partially) evaporate liquid components of the electrocatalyst composition. Parameters of the drying operation can be appropriately adjusted to achieve an appropriate consistency of the electrocatalyst composition for heat treatment (e.g., sintering) at block 312. Such parameters can depend on the ambient and conditions (e.g., humidity). As an example, the drying operation may be performed at a temperature between 80° C. and 120° C. for a period of 1 to 4 hours, such as 2 hours at 120° C. As another example, the drying operation may be performed at a temperature between 100° C. and 300° C. for a period of 1 to 4 hours, such as 2 hours at 200° C. The drying operation may be performed, for example, by placing the body in a drying oven or on a hot plate.

[0373] At block 312, a heat treatment (e.g., sintering) operation is performed, subjecting the body and deposited electrocatalyst composition to heat, thereby evaporating the liquid components of the electrocatalyst composition and causing the solid (e.g., particulate) components of the electrocatalyst composition to form porous regions of material (e.g., connected (e.g., sintered or partially fused) granular or particulate elements) containing the electrocatalyst for each half-reaction of the electrolysis, such that the porous regions occupy the open areas and form porous regions 117 of the body as described above with respect to the third and sixth examples of Figures 1d and 2c, respectively.

[0374] As a result of such heat treatment, the solid electrocatalyst components have been observed to occupy the open areas and bridge (ie, extend diametrically across) the open areas to form a porous medium.

[0375] The porous media may have an extent along its thickness that is less than the extent of the body, for example, this may result from the electrocatalyst composition partially penetrating through each open area during deposition.

[0376] The heat treatment (e.g., sintering) operation may be carried out by placing the body (with the electrocatalyst composition deposited thereon) in a temperature-controlled environment to subject the body to a treatment temperature for a treatment time. The temperature-controlled environment may be the interior chamber of a heater such as an oven or a muffle furnace (e.g., such as those available from Carbolite Gero, a subsidiary of the Verder Group (Verder International BV, Germany)).

[0377] The heat treatment (e.g., sintering) operation may be carried out by gradually increasing the treatment temperature over a heat-up phase of the treatment time. For example, the treatment temperature may be gradually increased to a peak temperature of 150°C to 1000°C. For example, the peak temperature may be 250°C to 800°C, 300°C to 600°C, 300°C to 450°C, e.g., about 350°C. In another example, the peak temperature may be 600°C to 1000°C, e.g., 700°C to 1000°C, or 800°C to 1000°C, or 900°C to 1000°C, or 900°C to 950°C, e.g., about 930°C.

[0378] The processing temperature may be gradually increased from a starting temperature, which may be, for example, an ambient temperature (e.g., room temperature) of 20° C. or a heater starting temperature such as 30° C., to a peak temperature. The heating rate may be 0.5-2° C. per minute, e.g., about 1° C. per minute. The heat treating (e.g., sintering) operation may include maintaining the processing temperature at the peak temperature for a holding period of processing time, e.g., 1-10 hours, e.g., 1-8 hours, or 1-6 hours, or 1-4 hours, or about 1 hour, or about 2 hours, or about 4 hours, or about 6 hours, or about 8 hours.

[0379] It will be appreciated that in some embodiments, sufficient drying of the electrocatalyst composition may occur during the heat-treating (e.g., sintering) operation itself, such that a separate drying operation (i.e., block 310) is not required. In such embodiments, the body may be subjected to a single heating operation that combines drying and heat-treating of the electrocatalyst composition.

[0380] The mechanism for forming porous regions of the material during the heat-treating operation may depend on the nature of the electrocatalyst composition, the treatment temperature, and the treatment time. The electrocatalyst particles may sinter or fuse together during the heat-treating operation, for example, by a diffusion process. Components of the electrocatalyst composition (e.g., a polymer binder) may melt and / or harden during the heat-treating operation, thereby bonding the electrocatalyst particles together. Chemical reactions (e.g., oxidation) may occur during the heat-treating operation, thereby forming reaction products (e.g., oxides) that bond the electrocatalyst particles together.

[0381] In trials of this method using electrocatalyst compositions containing particulate nickel, it was found that when heat treatment is carried out in an oxidizing atmosphere, peak treatment temperatures above 400°C can result in adverse oxidation of the electrocatalyst, producing excessive amounts of nickel oxide. However, the oxidation effect can be avoided by conducting the heat treatment operation in a controlled atmosphere that is substantially oxygen-free (e.g., an inert or reducing atmosphere), such as, for example, an atmosphere containing (e.g., consisting of) argon or nitrogen and / or hydrogen (e.g., a mixture of 95 wt% nitrogen and 5 wt% hydrogen). It will be appreciated that the level of oxidation of a given electrocatalyst composition can be controlled by varying the treatment temperature, treatment time, and / or atmosphere composition.

[0382] The method may include one or more secondary heat treatment operations performed subsequent to the primary heat treatment (e.g., sintering) operation at block 312. For example, the body may be placed in a temperature-controlled environment to subject the body to a secondary treatment temperature for a secondary treatment time. The temperature-controlled environment may be the interior chamber of a heater such as an oven or a muffle furnace (e.g., such as those available from Carbolite Gero, a subsidiary of the Verder Group (Verder International BV, Germany)).

[0383] The secondary heat treatment operation may be performed by gradually increasing the secondary treatment temperature over a heat-up phase of the secondary treatment time. For example, the secondary treatment temperature may be gradually increased to a peak temperature between 500°C and 1500°C. For example, the peak temperature may be between 750°C and 1200°C, between 800°C and 1000°C, between 850°C and 950°C, e.g., about 930°C.

[0384] The secondary heat treatment operation may be carried out in a substantially oxygen-free controlled atmosphere (e.g., an inert or reducing atmosphere), such as, for example, an atmosphere comprising (e.g., consisting of) argon or nitrogen and / or hydrogen (e.g., a mixture of 95 wt. % nitrogen and 5 wt. % hydrogen).

[0385] The secondary heat treatment operation may include (e.g., be) a stress relief heat treatment operation intended to relieve welding stresses within the body. Additionally or alternatively, the secondary heat treatment operation may be a secondary sintering operation, during which densification of the porous medium occurs, for example, by grain boundary diffusion.

[0386] In some examples, the heat-treating operation can be considered to include a first stage and a second stage. The first stage can be performed to pyrolyze or burn off non-electrocatalyst components of the electrocatalyst composition, such as the binder component of the electrocatalyst composition, and thus can be performed in an oxidizing atmosphere. The second stage can be performed to sinter the electrocatalyst-containing particles together and thus can be performed in an inert (or reducing) atmosphere, such as an atmosphere comprising (e.g., consisting of) argon or nitrogen and / or hydrogen. The first stage can be performed using a peak temperature of 150-500°C, e.g., 200-500°C, or 250-450°C, or 300-500°C, e.g., about 300°C or about 350°C. The second stage may be carried out using a peak temperature of 500-1000°C, for example 600-1000°C, or 700-1000°C, or 800-1000°C, or 900-1000°C, or 900-950°C, for example about 930°C. The first stage may last for 2-10 hours, for example 4-8 hours, for example about 6 hours. The second stage may last for 30-300 minutes, for example 30-90 minutes, for example about 60 minutes. Exemplary Electrocatalyst Compositions An exemplary electrocatalyst composition is a mixture of conductive ink available from Creative Materials Inc. (Massachusetts, USA) under the product designation 116-25 and solvent available from Creative Materials Inc. under the product designation 112-19.

[0387] Conductive ink 116-25 contains 50% to 70% by weight nickel fine particles (CAS number 7440-02-0), 30% to 50% by weight non-polar ester solvent, 5% to about 10% by weight polymer resin, and less than 2% by weight carbon black (CAS number: 1333-86-4). After curing for 5 minutes at 125°C, conductive ink 116-25 contains greater than about 84% by weight nickel. Conductive ink 116-25 has a specific gravity (measured against water) of about 2.21, a viscosity of about 25 Pa·s, a boiling point greater than about 196°C, and a flash point greater than about 100°C.

[0388] Solvent 112-19 is the same non-polar ester solvent found in conductive ink 116-25. It has a boiling point greater than about 196°C, a flash point of about 100°C, an upper flammability limit of about 8% by volume and a lower flammability limit of about 0.9% by volume, a vapor pressure of about 0.3 hPa at 20°C, a specific gravity of about 1.092 (measured relative to water), and an autoignition temperature of 370°C.

[0389] For example, various amounts of solvent (e.g., solvent 112-19) have been tested and found to provide a suitable viscosity to flow into the open area, with the remainder of the electrocatalyst composition consisting of the conductive ink (e.g., 116-25).

[0390] Thermogravimetric analysis was performed on three such electrocatalyst compositions, containing 5 wt%, 10 wt%, and 15 wt% solvent (112-19), with the remainder consisting of conductive ink (e.g., 116-25). The conductive ink and solvent were mixed by a biaxial centrifuge (DAC) at 2000 rpm for 2 minutes to form the electrocatalyst compositions. The solids content of the samples ranged from about 60 wt% (5 wt% solvent) to about 40 wt% (15 wt% solvent). The viscosity of each sample ranged from about 5 Pa·s (15 wt% solvent) to about 13 Pa·s (5 wt% solvent). The solids content and viscosity values ​​were measured at 25°C by a rheometry evaluation method performed at a shear rate of 1 l / s using 40 mm parallel plates with a 500 μm gap. Values ​​related to the solids content and viscosity of exemplary electrocatalyst compositions are reported in Table 1 below.

[0391] [Table 1]

[0392] As an alternative to solvent 112-19, solvents 102-03 and / or 113-12 (also available from Creative Materials Inc.) may be used to thin the conductive ink.

[0393] Solvent 102-03 includes about 90% to about 100% by weight of a proprietary diluent and about 0% to about 10% by weight of 2-butoxyethyl acetate. Solvent 102-03 has a boiling point greater than about 190°C, a flash point (in a closed cup) greater than about 90°C, a specific gravity (measured relative to water) of about 1.13, an autoignition temperature greater than 400°C, and a viscosity at 25°C of about 12 Pa·s to about 18 Pa·s.

[0394] Solvent 113-12 comprises about 95% by weight of 2-butoxyethyl acetate, which has a boiling point of about 192°C, a flash point of about 76°C, an upper flammability limit of about 8.54% by volume and a lower flammability limit of about 0.88% by volume, a vapor pressure of about 0.29 mmHg at 20°C, and a specific gravity (measured relative to water) of about 0.94. Example Heat Treatment Results Heat treatment (eg, sintering) performance was tested by fabricating representative porous walls according to the fabrication method described above with reference to Figure 3a.

[0395] In block 302, a porous-walled body was provided comprising a rectangular planar section of nickel-chromium alloy (specifically Inconel® alloy, Inconel® 600) having longitudinal dimensions of 50 mm, transverse dimensions of 50 mm, and thickness dimensions of 1 mm.

[0396] At block 306, a pattern of open areas was formed in the body by a laser drilling process as described above. The open areas were formed through the entire thickness of the body using a millisecond laser operating at 500 Hz. The open areas were formed elongated along a path at a 70° inclination angle to the longitudinal direction (and therefore at a 20° angle to the thickness direction of the planar body). The open areas were drilled in laterally offset rows to form a regular grid pattern with equal lateral and longitudinal pitch.

[0397] At block 308, an electrocatalyst composition corresponding to that described above (5 wt. % solvent variant) was applied using an applicator as described above.

[0398] In block 310, a drying operation was performed in which the body (and deposited electrocatalyst composition) was maintained at 120° C. on a precision hotplate for two hours.

[0399] At block 312, a heat treatment operation was performed to form a porous wall having a porous region extending through the body. The heat treatment operation was performed using a muffle furnace and consisted of 1°C / min ramp steps to increase the treatment temperature from a starting temperature of 30°C to a peak temperature of 350°C, which was maintained for a 3 hour hold time.

[0400] Figures 4a-4d show SEM (scanning electron microscope) images of one side of a porous wall at various fabrication levels, with scales ranging from 100 μm (Figure 4a) down to 10 μm (Figure 4d) indicated on the drawings. Figure 4a shows the ends of four porous regions terminating on one side of the body. Figures 4b-4d show the porous media within the porous regions, generally depicting a porous structure formed by partially sintered (e.g., fused) granular or particulate elements (comprising nickel in this example) that define open spaces between them. As can be seen in Figures 4b-4d, although the spacing between the granular or particulate elements appears to vary, there is no directional configuration of the elements that would significantly bias flow in a particular direction.

[0401] 5 shows a flow chart of a method 500 for manufacturing a porous wall according to the third example of FIG. 1 d by additive manufacturing, and will be described with reference to features of the porous wall of that example (using reference numbers associated with that example). The method is for manufacturing a porous wall layer-by-layer (or slice-by-slice) in which a build material (e.g., a powder) is deposited on a bed or platform in successive layers, and the successive layers are progressively and selectively heat-treated (e.g., sintered or melted) to form slices of the porous wall.

[0402] In block 502, model data for additive manufacturing of a porous wall, e.g., by selective laser sintering (SLS), particularly laser powder bed fusion (L-PBF), is provided to control an additive manufacturing apparatus. The model data corresponds to the example porous wall 110 described above with respect to FIG. 1d, which includes a body 116 and a plurality of discrete porous regions 117 as described above. For example, the model data may define the geometry of the body 116 and the geometry of the porous regions, and may define a porosity (or a porosity-related parameter) that is variable between the body 116 and the porous regions 117. For example, the model data may be defined such that a parameter (e.g., porosity or a porosity-related parameter) is assigned to a discrete region of the model (e.g., a region assigned an identity for parameter attribution), or such a parameter may be applied to a subregion or point of the model or a matrix of such subregions or points (e.g., voxels of the model or pixels of a slice of the model) that belong to a continuous distribution and are not specifically assigned to a region for parameter attribution. The parameter may be defined as porosity or a related parameter (eg, energy density) that has a relationship to the porosity formed (ie, the porosity manifested in the manufactured component).

[0403] In block 504, a controller of the additive manufacturing device controls the additive manufacturing device to form the porous wall based on the model data. Suitable types of additive manufacturing devices are understood in the art, and a schematic depiction of such devices in a drawing is not considered necessary to aid in understanding the additive manufacturing process. By way of example only, the device may be configured to perform an LPBF process. An exemplary commercially available product is the EOS M400-4 additive manufacturing machine available from EOS GmbH, Germany. A further example of a commercially available product is the Renishaw AM400 or AM500 machine, a pulsed laser machine available from Renishaw plc, UK. Either machine may be used with any suitable electrocatalyst, as described elsewhere herein, such as, for example, a nickel or nickel alloy build material (such as a nickel-chromium alloy, e.g., Inconel® 600). A suitable particle size distribution of the build material may be 15-45 μm.

[0404] The model data may be preprocessed to provide layer-by-layer instructions to the additive manufacturing device. The preprocessing may be performed by the controller of the additive manufacturing device or a separate controller. For example, the layer-by-layer instructions may define, for each layer of build material to be heat-treated (e.g., sintered) to form porous walls, one or more laser control parameters, including any or all of: (i) the path of the laser over the layer to form each slice of the porous wall; (ii) the laser scanning speed; (iii) the scanning spacing (also known as the hatch distance) between adjacent (adjacent) segments of the laser's path; (iv) the laser energy; and (v) the laser spot size. Any or all of the laser control parameters may be controlled to vary the energy density applied to the layer and thereby control the amount of melting of the build material. In particular, the extent to which particles of the build material are melted depends on the applied energy density, and the melting depth may depend on the energy density (i.e., the depth into and below the active layer that undergoes melting by the action of the laser, which may be greater than the height of the layer of build material as deposited on a bed or platform for the active layer).

[0405] Pretreatment may be performed to vary the or each laser control parameter to compensate for laser penetration and / or heat transfer that may otherwise occur to cause excessive melting in areas intended to be porous. For example, when melting build material in an active layer to form a solid (e.g., non-porous) portion corresponding to the body 116 of the porous wall that overlaps a portion (which may be partially melted or unmelted) of a previous layer corresponding to the porous region 117 of the porous wall, the laser may penetrate through the active layer and / or heat generated by the laser in the active layer may conduct to the previous layer, causing excessive melting. Pretreatment may define layer-by-layer instructions to compensate for (e.g., mitigate) such excessive melting effects by, for example, determining or scaling back the energy density for forming the solid portion (corresponding to the body 116) in layer n based on a determination that the respective portion in layer n overlaps a partially melted or unmelted portion (corresponding to the porous region 117) in layer n-1 (the notation "n," "n-1," etc. indicates successive layers). Pretreatment may be performed to determine whether the energy density for forming the solid portion in layer n can be reduced (e.g., relative to a typical or standard energy density for forming a solid portion) based on a determination that laser penetration and / or heat transfer from melting of the solid portion in the upper layer n+1 affects melting of the build material in layer n to provide a target degree of melting. For example, pretreatment may be performed to gradually vary the energy density across multiple layers, locally to transitions between regions having different porosity-related parameters (e.g., different target porosities corresponding to the body and porous regions, respectively).

[0406] In addition to or as an alternative to any pre-processing based on layer-by-layer analysis of laser penetration and / or heat transfer, pre-processing may be performed to determine buffer regions of the body adjacent to porous regions and apply parameters for control of the additive manufacturing process (e.g., porosity or related parameters as described above) to reduce the energy density applied in the buffer regions relative to the energy density through the remainder of the body. Such parameters may be assigned or attributed to discrete regions identified in the model data or instructions, or to respective sub-regions (e.g., voxels or pixels) as described above.

[0407] As shown in FIG. 5, block 504 includes repeating a loop that dispenses layers of build material (block 506) and controls selective melting of the build material based on model data and / or layer-by-layer instructions (block 508).

[0408] Optionally, at block 510, the method includes a heat treatment process performed after the additive manufacturing process, whereby the porous walls formed by the additive manufacturing process are heated in a temperature-controlled environment. The heating may be performed to melt any unmelted or partially melted build material in the model, and the temperature and treatment time of the heat treatment process may be determined to achieve a desired degree of such melting based, for example, on best practices understood in the art and appropriate trials. Such a heat treatment process may alternatively be referred to or understood in the art as a curing process.

[0409] Optionally, at block 512, the method includes a finishing process. This may include machining to remove excess build material from the porous walls. The finishing process may be performed to achieve a target size and shape of the porous walls. The finishing process may be performed, for example, to selectively remove material on the outer surfaces of the porous walls.

[0410] Any suitable materials of construction can be used in the additive manufacturing process. Suitable materials of construction containing electrocatalysts for each half-reaction of the electrolysis include (e.g., consist of) nickel or a nickel-based alloy, such as a nickel-based superalloy. A suitable example is a nickel-chromium alloy, such as an Inconel® alloy (e.g., Inconel® 600). Such materials may be suitable electrocatalysts for catalyzing the electrolysis half-reactions at the anode and for the aqueous electrolyte at the cathode.

[0411] Figure 6 shows an image of a cross section of a sample porous wall produced by the additive manufacturing process described above. The sample porous wall was cut to expose a cross section through multiple porous regions. The gradation of the porous regions can be observed within the body (manifesting a substantial lack of porosity). The porosity of the porous regions can be observed by the distribution of porous media within the cross section.

[0412] The image shows the curvature of the cut porous wall resulting from the pressure applied in the imaging mounting press.

[0413] Heat treatment (e.g., sintering) performance was tested in a further example. In this example, a rectangular, planar section of a nickel-chromium alloy (specifically, Inconel® alloy, Inconel® 600) was coated with an electrocatalyst composition (5 wt. % solvent variant) corresponding to the exemplary electrocatalyst composition described above. A drying operation was performed in which the plate (and the deposited electrocatalyst composition) was maintained at 120°C for 2 hours on a precision hotplate. A two-stage heat treatment operation, as described above, was then performed using a muffle furnace. In the first stage, performed in an oxidizing atmosphere, the plate was heated from room temperature to a peak temperature of 300°C at a rate of 5°C per minute, and the plate was held at the peak temperature for 6 hours. In the second stage, performed in an argon atmosphere, the temperature was increased to 930°C, and the plate was held at that temperature for a 15-minute hold time. 19 shows three subsequent SEM (e.g., scanning electron microscope) images (a)-(c) taken at 1000x magnification of different regions of the porous media formed during sintering of the electrocatalyst composition. The porous sintered structure is evident. simulation Figure 7 shows an axisymmetric model geometry 700 of a flow simulation model of an electrolytic cell having the flow configuration described above with respect to the exemplary flow configuration 100 of Figure 1 a. Reference numbers corresponding to the flow configuration 100 as described in connection with Figure 1 a, including those of the annular inlet chamber 102 and inlet 101, the first and second porous walls 110 and 120, the inner and outer outlet chambers 130 and 140, are also provided for corresponding features shown in Figure 7.

[0414] The flow simulation model has a vertical orientation such that its longitudinal axis A is vertically oriented and gravity is downward in the drawing orientation.

[0415] The geometry of the upstream inlet manifold 702 and downstream outlets 730, 740 as implemented in the flow simulation model differs slightly from the equivalent physical features shown in FIG. 1 a to reduce any flow effects local to the inlet and outlet boundary conditions in the model that adversely affect flow through the inlet chamber 102 and outlet chambers 130, 140 of the flow simulation model.

[0416] The inlet manifold 702 is upstream of the annular inlet 101 to the inlet chamber 102 and has a length l inflow The inlet manifold 702 extends downwardly only to allow the inlet flow to develop from the inlet boundary 701 at its upstream end towards the inlet flow. The inlet manifold 702 includes a conical flow dividing wall at an angle of 30° to the longitudinal direction A to provide flow to the annular inlet 101 of the inlet chamber 102.

[0417] The downstream outlets 730, 740 are downstream of the respective longitudinal portions of the outlet chambers 130, 140 that are laterally / radially adjacent to and extend longitudinally beyond (e.g., above) the porous walls 110, 120. The downstream outlets 730, 740 each have a length l outflow and terminate at respective outflow boundaries 732, 742. The outflows are provided to separate the outflow boundaries 732, 742 of the model from portions of the model that include porous walls, e.g., to reduce any effect of a particular outflow shape on that portion of the model.

[0418] The flow simulation model is consistent with the set of electrolytic cell dimensions listed in Table 2 below.

[0419] [Table 2]

[0420] Simulations of flow within the flow simulation model were performed, including simulations with electrolytic reactions. Simulations of various sets of conditions using the flow simulation model are referred to interchangeably herein as "simulations" or "simulation cases." Simulations are performed to evaluate flow patterns associated with the diffusion and crossover of species (e.g., electrolyte solutions and their respective reaction products).

[0421] Simulations were performed using simulation software provided by COMSOL Multiphysics® 5.6, developed by COMSOL AB, Sweden.

[0422] The flow simulation model is defined to reflect the following assumptions: Hydrogen-oxygen-water mixtures with NaOH electrolyte are fully miscible and supercritical single-phase at all conditions of interest (e.g., pressure > 22 MPa, temperature > 380°C); Inlet flows to the electrolyzer of up to 40 g / min remain laminar within the electrolyzer at operating conditions.

[0423] The flow simulation model models the diffusion of the components of a hydrogen-oxygen-water mixture. Density and viscosity are modeled as a function of local composition and pressure for a reference temperature of 400°C. The flow simulation model is defined to model fluid flow using the weakly compressible Navier-Stokes equations, including gravity (to model buoyancy). The flow simulation model is defined to solve for steady-state flow conditions. The simulation is isothermal.

[0424] The flow simulation model models the inlet boundary 701 as a fully developed (parabolic) laminar flow profile at a specified mass flow rate. The flow simulation model for the simulation examples models the outlet boundaries 732, 742 as constant outlet pressure boundaries (at 23 MPa). A no-slip condition is applied to the walls of the model chamber. In each of the simulation examples described below, the inlet flow is modeled at a pressure of 23 MPa, and all species are modeled at that pressure and a temperature of 400°C (134 kg / m -3 The solubility of the solubility-in-water mixture is modeled using properties corresponding to a density of water of 1000 kJ / cm², corresponding to a viscosity of 27.4 μPa.

[0425] The flow simulation model models the porous wall 110 as a porous medium with porosity parameters applied to reflect the configuration of the particular flow simulation instance (e.g., whether it is an isotropic porous wall as in the example of Figures 1b and 2a, an anisotropic porous wall with open channels as in the example of Figures 1c and 2b, or a porous wall with a discontinuous porous structure optionally extending along a path with a longitudinal component as in the example of Figures 1d and 2c).

[0426] Referring to the flow simulation examples described above, or those in which each porous wall has a sloped channel or a sloped, discontinuous porous structure, a porosity parameter is applied to reflect the directionality of the porous medium. In particular, the flow simulation model implements a (variably oriented) structured mesh to simulate flow through the electrodes, and this mesh is aligned with the path angle of each channel or porous region. In each model, the porous region is simulated as a homogenized porous medium by applying (e.g., simulating) a Brinkman force. The associated permeability tensor is adjusted to correspond to the path angle of each simulation example. In particular, the associated permeability value is set along the path of each channel or porous region (i.e., the path along which the respective channel or porous region is elongated) and is set to a null (zero) value in the direction perpendicular to the path. Thus, the model provides constraints on the porous flow corresponding to each channel or porous region. The porosity parameter is set as 1 for simulation examples with open channels and using a value between 0 and 1 (as described below) for simulation examples with porous regions (i.e., discontinuous porous structures).

[0427] The flow simulation model is defined such that each electrolysis (e.g., hydrolysis) half-reaction is simulated to occur within the porous walls 110, 120 at a variable rate corresponding to the availability of electrolyte at that location and the applied current. Thus, the flow simulation model is capable of simulating flow patterns and species distributions corresponding to electrode water depletion effects, as described below. In particular, electrode water depletion effects can occur when the porous wall configuration is such that the inlet electrolyte is biased to flow through a proximal portion of the porous wall (i.e., a longitudinal portion of the porous wall relatively closer to the inlet 101), resulting in a relatively lower proportion of electrolyte flowing through a distal portion of the porous wall, which correspondingly reduces the rate of each half-reaction and the rate at which each reaction product is produced in the model. This can serve to limit the sustainable current for the electrolysis reaction.

[0428] The flow simulation model simulates the reaction using sources and sinks of the respective fluid reaction products in the porous walls 110, 120.

[0429] A simulation example shows 1.42 kg.h for 150 cells in parallel. -1 is defined to reflect an operating current of 250 A, which can correspond to a target hydrogen production rate of 100 kJ / s.

[0430] The inventors performed simulations of four baseline configurations to evaluate selected flow phenomena and effects as discussed herein. The four baseline configurations are referred to herein as follows:

[0431] Configuration A: Isotropic porous wall corresponding to the example in Figure 1b (for example, or to the example in Figure 2a).

[0432] Configuration B: Porous wall with open channels corresponding to the examples of Figure 1c or 2b to provide an anisotropic porous structure. The channels may be oriented perpendicular to the longitudinal direction of the porous wall, or the channels may extend along a path that is elongate in the longitudinal direction (i.e., have a longitudinal component).

[0433] Configuration C: Porous wall with discontinuous porous structure corresponding to the example in Figure 1d.

[0434] To enable a comparative study of the simulations of each of the configurations A to C, various parameters are defined for the simulation as described below. Before that study, the relevant parameters are considered.

[0435] Porosity is a measure of the percentage of the porous wall that is open to allow flow therethrough, and conforms to standard usage of the expression in the art.

[0436] In the flow simulation model, the entire longitudinal extent of the porous wall is configured for flow therethrough. It will be appreciated that in other embodiments, the porous wall may include one or more substantially non-porous longitudinal portions not intended for flow therethrough, for example at the proximal or distal ends of the porous wall (e.g., for coupling to respective electrical terminals of the electrolyzer cells), and longitudinal porous portions corresponding to the porous wall in the flow simulation model. Thus, the terms porosity and the related term "macroporosity" as used herein refer to the respective properties measured / defined over the longitudinal porous portion of the porous wall.

[0437] Macroporosity is a measure of the percentage of the open portion of a porous wall defined by channels therethrough (e.g., Configuration B), and also of the open portion of a body of porous walls having discrete porous regions (e.g., Configuration C). With reference to Configuration C, macroporosity is the porosity when the porous media within a porous region has been removed, or the porosity of the precursor / intermediate product before porous media is introduced into the corresponding open regions.

[0438] The macropattern corresponds to the configuration of channels / porous regions within the porous wall, which may be, for example, a regular matrix of channels / porous regions arranged in columns or rows, or with laterally / circumferentially offset rows. For example, in a hexagonal configuration, the rows are such that for each channel / porous region, there are six surrounding channel / porous regions distributed at 60° angles within the local plane / surface of the respective wall, with a substantially uniform separation / pitch for each surrounding pore. In a regular grid pattern, the channels / porous regions of successive rows are not laterally / circumferentially offset.

[0439] The pitch corresponds to the separation between the centers of the channels (Configuration B) and porous regions (Configuration C) as evaluated at the inlet side of each porous wall. For porosity patterns with unequal separation in different directions (e.g., in a regular lattice with columns and rows, where the diagonal distance is longer), the pitch is the shortest such separation. In each of the simulations described below, the circumferential pitch is the shortest separation and is generally referred to as the circumferential pitch (or circumferential pitch). This may also be defined by referring to the number of paths per periphery ("paths per periphery").

[0440] The pitch height corresponds to the separation between each row of channels (Configuration B) and porous regions (Configuration C).

[0441] Microporosity is a measure of the porosity within the porous region 117 in configuration C (e.g., Figures 1d and 2c). The porosity of the porous wall as a whole can be calculated as the product of the macroporosity and the microporosity.

[0442] A pathway refers to a channel (Configuration B) or porous region (Configuration C) that extends through and along the body of the porous wall.

[0443] The path diameter is the diameter of the path of the channel (Configuration B) or porous region (Configuration C) corresponding to the substantially circular profile of the respective channel or porous region.

[0444] The number of paths defines the number of channels (Configuration B) or porous regions (Configuration C) through each body of the porous wall. This is regardless of the network of flow paths within each porous region in Configuration C; in contrast, each porous region in Configuration C corresponds to a single path.

[0445] The path angle is the angle at which the path is inclined from the longitudinal axis. For example, a path angle of 70° corresponds to a path extending along the longitudinal direction offset by 70° from the longitudinal direction and 20° from the orthogonal direction (radial or thickness direction).

[0446] For each of the simulation cases described below, the inner (first) porous wall serves as the cathode (for hydrogen production) and the outer (second) porous wall serves as the anode (for oxygen production).

[0447] The inventors have defined simulation cases for the simulation model to evaluate various flow effects, phenomena, and trade-offs associated with the baseline configuration, and an introductory discussion of these and related terms will aid in the interpretation of the simulation results.

[0448] The inventors have observed that in flow configurations with axisymmetric configurations (i.e., of concentrically arranged porous walls), there tends to be a flow bias towards the outer chamber when the porous walls have similar configurations, and the expression "flow bias" refers to a preferential tendency for flow to be in one direction (i.e., a relatively higher mass flow rate in one direction than in another). This is believed to be because the outer porous wall has a larger radius and therefore a larger surface area / volume for the flow to pass through, and therefore presents a lower resistance to flow when the porous features are similarly provided (e.g., an equal distribution of similarly sized channels).

[0449] In the context of electrolytic cell flow configuration, equal flow distribution may not be desirable given the stoichiometry of each electrolytic half-reaction at the two electrodes. For example, a larger proportion of electrolyte solution may be required at one electrode than at the other to carry out each electrolytic half-reaction at a mutually sustainable rate. Thus, while mass flow bias is not necessarily undesirable, flow bias may be excessive or undesirable in either direction if it has the effect of promoting species crossover (i.e., the flow of fluid reaction products across the separating gap between the two electrodes).

[0450] The inventors have found that undesirable flow biases can be mitigated by providing porous walls with different properties that affect their flow resistance (e.g., porosity, cross-sectional area or diameter, and diameter of the paths through the porous medium). For example, the outer wall can be made relatively less porous (e.g., by controlling porosity or by reducing the number of paths, path diameter, or increasing the path angle), or the inner wall can be made relatively more porous.

[0451] The inventors have also observed that fluid reaction products tend to diffuse across the inlet chambers, so that, for example, fluid reaction products produced at the cathode reach the anode and are released through the respective outlet chambers. Flow bias within a flow configuration can either act with (e.g., multiply) or act against (e.g., mitigate) the diffusion of species.

[0452] Fluid reaction products may have different diffusivities. The inventors have found that for electrolysis of aqueous electrolyte solutions to produce hydrogen and oxygen, hydrogen has a higher diffusivity than oxygen. When the inner porous wall serves as the cathode, hydrogen production occurs at the inner porous wall, and therefore diffusion of hydrogen in the radially outward direction toward the outer porous wall should be mitigated.

[0453] One way to mitigate species diffusion in a particular direction is to affect or provide a neutral flow bias or to bias the flow in the opposite direction, however, this may result in favoring any diffusion of another fluid reaction product (e.g., favoring the diffusion of oxygen produced at the radially outer anode toward the radially inner cathode) and may deprive the opposite electrode of electrolyte fluid for the respective half-reaction of the electrolysis.

[0454] Apart from the flow bias effect, the inventors have observed that the flow resistance provided by the porous walls can affect the distribution of electrolyte liquid flow through the inlet chamber and the respective porous walls. As discussed elsewhere herein, the porous walls provide a flow resistance such that a pressure difference across the wall is required (or established) for flow therethrough. When a porous wall has a relatively low flow resistance (e.g., a relatively high flow coefficient K V), the flow rate of fluid along any particular path from the inlet through the porous walls to the outlet may be governed by (i.e., primarily determined by) other characteristics of the flow path outward from the walls. For example, when there is a relatively small separation gap between the electrodes, the frictional (e.g., viscous) forces in the inlet chambers may be relatively higher than the frictional (e.g., viscous) forces in the respective outlet chambers. Thus, when naturally flowing along the path of least resistance through the electrolytic cell, the electrolyte liquid may tend to flow preferentially through the proximal portion of each porous wall (i.e., the portion relatively closer to the inlet) and may benefit from the lower frictional (e.g., viscous) forces in the outlet chambers, resulting in higher mass flow and velocity flow rates through the proximal portion of each porous wall. This may result in the electrolyte liquid being "starved" at each porous wall, corresponding to the distal portion of the porous wall being deprived of a supply of electrolyte liquid for carrying out each half-reaction of the electrolysis. As mentioned above, such uneven flow of electrolyte liquid may occur when the porous walls provide a relatively low flow resistance.

[0455] In contrast, when a porous wall provides a relatively higher flow resistance, frictional (e.g., viscous) forces within the porous wall itself become more dominant in relation to the total forces experienced from the inlet to the outlet of the flow configuration / electrolyzer, reducing local peaks in flow velocity (and mass flow rate) along the porous wall and providing a more uniform flow (especially since resistance forces are proportional to the square of the velocity).

[0456] The flow bias effect may also be exacerbated by relatively low flow resistance. In particular, when the porous walls generally provide relatively low flow resistance, it is believed that a relative change in the flow resistance provided by one of the walls may result in a significant change in the flow bias. Thus, it is believed that selecting conditions for maintaining a desired flow bias may be relatively more difficult when one or more of the porous walls provide relatively low flow resistance.

[0457] In regard to providing an efficient flow configuration for electrolysis, the inventors have determined that it may be desirable to maximize the surface area of ​​the porous wall that is exposed to the electrolyte solution and that is electrocatalytically active for each half-reaction of the electrolysis. The inventors have also determined that it is desirable to reduce the separating gap between electrocatalytic regions of the porous wall.

[0458] The inventors have realized that instead of providing the porous wall as an isotropic porous medium (i.e., configuration A as defined above), one or more channels can be provided through the porous wall to provide porosity in the wall (e.g., configuration B). By selecting the parameters of the channel (e.g., path diameter, path angle, thickness), properties related to flow bias and flow resistance can be controlled.

[0459] The inventors also envisioned that such channels could be provided as inclined channels, as described herein. In particular, because the fluid reaction products of each half-reaction of the electrolysis are less dense than the electrolyte solution, their generation within the respective channels could establish a buoyancy-driven flow directed upward toward the respective outlet chambers 130, 140, thereby inhibiting any backflow of the fluid reaction products generated within the channels (Configuration B). This is because such flow would be opposite the direction of the dominant buoyancy-driven flow through the respective porous walls. Thus, the inclination would prevent species crossover (in either direction).

[0460] However, there may be trade-offs between various factors, including manufacturability, reactive surface area, flow resistance to prevent depletion, and providing flow resistance for appropriate flow bias.

[0461] For example, it is contemplated that open channels according to configuration B may be formed with a relatively small path diameter to reduce porosity and provide a relatively large flow resistance to avoid depletion effects and susceptibility to flow bias. However, it is also contemplated that channels with a relatively larger path diameter may be more practical and cheaper to form.

[0462] In contrast, channels with relatively larger path diameters may be more practical and inexpensive to form, but they are associated with relatively lower flow resistance. The flow resistance of porous walls can be improved by providing relatively fewer channels, but this is associated with a reduction in the surface area available for electrolytic reactions within the channels.

[0463] The inventors have determined that by providing a discontinuous porous structure of configuration C (e.g., according to the examples of Figures 1d and 2c), good performance with respect to each of the trade-off factors discussed above can be achieved. In particular, rather than forming channels, discrete porous regions are formed that allow flow through the porous walls, with each porous region defining a network of flow paths through the porous medium. The porous regions can be formed with relatively large path diameters (e.g., corresponding to the diameter of the open regions, as discussed above, prior to providing the porous medium), yet because the porous medium is filled with the porous medium, adverse effects such as low flow resistance and low reaction surface area can be avoided. Furthermore, the porous regions can be angled (e.g., having a path angle of less than 90° relative to the longitudinal direction) to provide upward buoyancy-driven flow through the porous regions, thereby suppressing backflow of fluid reaction products.

[0464] Table 3 below defines the simulation settings for a first set of simulations to evaluate the effect of providing a tilt angle to the porous region of configuration C. The notation Simulation ID SxRy-Z corresponds to set x, run y - configuration Z. For example, the second run of this first set of simulations has configuration C and therefore has the ID S1R2-C. In the table and the discussion below, several values ​​are provided for both the inner and outer porous walls using the separator " / ", e.g., 70° / 70° indicates a path angle of 70° for each porous wall.

[0465] [Table 3]

[0466] In Table 3, the molar crossover concentration is reported relative to the molar concentration of each fluid reaction (e.g., hydrogen) product in the resulting fluid reaction product mixture (e.g., hydrogen and oxygen), excluding any residual electrolyte (e.g., water). This reflects the molar concentration in the fluid reaction product mixture that may be separated from the electrolyte at each outlet (as further explained below). The same applies to other values ​​of molar crossover as reported herein. In contrast, the molar concentrations shown in the figures are local molar concentrations (e.g., in the hydrogen-oxygen electrolyte mixture).

[0467] As shown in Table 3 by comparing the results for S1R1-C and S1R2-C, the effect of providing the porous region at an angle of 70° to the longitudinal direction, as opposed to the orthogonal direction (at 90°), is that the crossover performance improves for both hydrogen (H2) crossover to the outer outlet chamber and oxygen (O2) crossover to the inner outlet chamber.

[0468] Figures 8a-8c show contour plots of the hydrogen molar concentration (Figure 8a), oxygen molar concentration (Figure 8b), and water molar concentration (Figure 8c) for simulation case S1R2-C, corresponding to both porous walls with a graded discontinuous porous structure, with a path angle of 70° from the longitudinal direction and porosity values ​​of the first (inner) and second (outer) porous walls of 0.1 / 0.11.

[0469] As shown in FIG. 8a, contour lines in 0.001 molar increments of oxygen indicate increasing concentrations of oxygen within the outer porous wall 120 where each half-reaction of the electrolysis takes place, while the lack of any contour lines of oxygen within the inlet chamber 102 and inner porous wall 110 indicates very low oxygen crossover.

[0470] Similarly, as shown in FIG. 8b, contour lines at 0.005 molar hydrogen increments indicate increasing concentrations of hydrogen within the inner porous wall 110 where each half-reaction of the electrolysis takes place, but only the lowest contour line extends (towards the top) through the inlet chamber 102 and the outer porous wall 120, thereby indicating low hydrogen crossover.

[0471] In Figure 8c, the contours at 0.05 molar increments of water show a single contour within the first (inner) porous wall 110, indicating that the electrolyte solution is not depleted along the longitudinal extent of the porous wall.

[0472] A simulation example of configuration B was run, with the same channel diameter, channel angle, and porosity as simulation example S1R2-C. This simulation example matched the overall porosity by reducing the number of channels within each electrode. For the characteristic combination of parameters selected, a depletion effect was predicted to occur, thereby limiting the electrolysis reaction (e.g., limiting the current below the 250 A target). This may demonstrate that, despite similar overall porosity, a porous wall configuration with open channels may provide a lower flow resistance effect than a porous wall configuration with a discontinuous porous structure as described herein, resulting in undesirable flow bias and / or depletion effects.

[0473] The inventors have found that it is possible to adjust the flow bias by varying one or more parameters (as discussed further herein), and this was done to limit depletion effects and enable simulation of a flow configuration with porous walls according to Configuration B at a target current of 250 A. By way of example only, in a second set of simulations ("Set 2"), the porosity of the inner wall was increased and the porosity of the outer wall was reduced to suppress the flow bias towards the outer wall. The model settings for Set 2 are shown in Table 4 for simulations in both Configurations B and C. The flow results are shown in the accompanying figures.

[0474] [Table 4]

[0475] Figure 8d shows the flow split between the inner and outer outlets of the model for both simulation models over the flow rate range of 20 to 4040 g / min. Figure 8e shows the hydrogen and oxygen crossover (mol %) at the same flow rates.

[0476] The simulation results show that increasing the porosity of the inner porous wall and decreasing the porosity of the outer porous wall biases the flow toward the inner outlet of the flow simulation model at all flow rates (see Figure 8d). This is more pronounced in the simulation of configuration B, which has significant oxygen crossover and low hydrogen crossover, as shown in Figure 8e. In contrast, the simulation of configuration C shows slightly higher hydrogen crossover and very low oxygen crossover.

[0477] Although the porosity of the inner porous wall is higher in S2R2-B than in S2R1-C, which may drive a larger flow bias toward the inner outlet chamber, the porous wall according to configuration B generally provides lower flow resistance, resulting in significantly more pronounced crossover effects in the direction of the flow bias. Therefore, it is possible that a flow configuration with open channels, such as in configuration B, is more sensitive to flow bias compared to the flow configuration with the discontinuous porous structure of configuration C.

[0478] In addition to comparing the flow results and phenomena with different configurations of porous walls, we performed a parametric study by simulation to evaluate the effect of varying selected parameters of porous walls with discontinuous porous structure.

[0479] These parametric studies include:

[0480] i. Parametric study of dissimilar porosities of inner and outer porous walls.

[0481] a. With further sweeps of dissimilar path angles.

[0482] ii. Parametric study of path diameter.

[0483] iii. A parameter sweep of microporosity (which can be thought of as equivalent to different particle sizes).

[0484] iv. Comparison of results at two different electrode lengths.

[0485] As mentioned above, for flow configurations having angular configurations as described herein, if the porous walls each have a similar configuration, the outer porous wall will have a larger area and therefore naturally provide a lower flow resistance. The inventors have performed flow simulation models with dissimilar porosities of the inner and outer porous walls, as implemented by varying the number of channels (i.e., the number of porous regions) within each wall. Certain embodiments vary the number of channels by varying the circumferential pitch of the porous regions, which may represent either a pitch height variation or a uniform pitch.

[0486] The geometry and configuration of the flow simulation model was as described above with respect to FIG. 7, with the porous walls having a discontinuous porous configuration (Configuration C) and a path angle to the longitudinal direction of less than 90°.

[0487] (i) For the dissimilar porosity sweeps, the porosity of each wall was varied by adjusting the number of paths in each porous wall, without changing the path diameter (120 μm) or the microporosity associated with each porous region. Figures 9a-d show four matrices of sweep results for each combination of angles. The path angles are relative to the longitudinal direction.

[0488] The results are presented in categories numbered 1, 2, 3, and X. These categories relate to compliance with the crossover threshold, known in the art as the lower explosive limit (LEL). For each combination of porosity shown for each matrix, flow simulations were performed at several different inlet mass flow rates between 20 and 40 g / min.

[0489] Category 1 corresponds to both outlets having a crossover corresponding to an LEL of 50% or less for at least one flow rate in the flow rate set. Category 2 corresponds to both outlets having a crossover corresponding to an LEL of 100% or less. Category 3 indicates that a simulation was performed but did not meet the requirements of Category 1 or 2. Category X indicates that a simulation was not performed.

[0490] As can be seen, in this particular example (i.e., with a particular definition of the flow simulation model conditions), the results indicate that the porosity of the outer porous wall should be reduced relative to the porosity of the inner porous wall to provide a flow bias that yields adequate results; as the porosity of the outer porous wall increases, less satisfactory results are achieved. Reducing the inner porous wall angle from 70° to 50° did not affect the results as reported (by comparing the matrices in Figures 9a and 9b). However, reducing the outer porous wall angle from 70° to 50° and then to 30° results in more cases tending to fall into categories 1 and 2.

[0491] In addition to any buoyancy-related crossover reduction effect of the angle reduction relative to the longitudinal direction, the angle reduction increases the path length through each electrode, and therefore increases flow resistance, thereby further limiting or reversing the flow bias toward the outer porous wall.

[0492] The above results demonstrate how flow resistance across a porous wall can be independently varied, for example, by varying the number of paths and / or by varying the path angle. It should be appreciated that the results are presented by way of example only, and that any optimal combination of parameters may be specific to a particular porous wall geometry, with different optimal combinations being suitable for other geometries. For example, flow bias may be affected in additional different ways within a flow configuration and can be reduced or controlled by increasing or decreasing variations in porosity and / or path angle. In this context, it should be appreciated that additional factors that may affect flow bias may include differences in outlet pressure at the outlet, differences in wall thickness of the porous wall, different geometries of the outlet chamber, etc.

[0493] Figures 9a-9d show the results of a further parametric study evaluating the effect of varying both the porosity and path angle of a porous wall with a discontinuous porous structure. The parametric study involves a baseline configuration in which the inner and outer porous walls have porosities of 0.1 and 0.11, respectively, and the porous region has a path angle of 70° (relative to the longitudinal direction). In this parametric study, the porosity is varied to 0.1 and 0.05, respectively, and the path angle of the outer porous wall is varied to 50°. Table 5 below shows the simulation settings for the parametric study.

[0494] [Table 5]

[0495] Figures 10a and 10b show the mass flow split between the inner and outer outlets of the flow simulation model for each simulation case at various flow velocities. As shown, the effect of changing the path angle of the outer porous wall on the flow velocity split between the inner and outer outlets is to bias the flow more toward the inner outlet (at each flow velocity). This indicates that reducing the path angle from 70° to 50° increases the flow resistance at the outer porous wall. By comparing Figures 10a and 10b, a similar effect is observed for reducing the porosity of the outer porous wall from 0.11 to 0.05. These results further demonstrate how flow bias can be adjusted by varying such parameters.

[0496] Figures 10c and 10d show the species crossover (molar fractions of hydrogen and oxygen, excluding water) trends at flow rates of 20, 30, and 40 g / min for each of the simulation cases defined in Table 5 above. There is a general trend of decreasing crossover with increasing flow rate. This may result from increasing the inertia of the flow through the porous wall, thereby preventing backflow of fluid reaction products. Figure 10c shows hydrogen crossover. From Figure 10c, it can be observed that variations that tend to bias the flow toward the inner porous wall, which is the hydrogen-producing cathode, tend to reduce hydrogen crossover in the outer outlet chamber and outflow. In particular, hydrogen crossover is reduced by a 50° path angle change in the outer porous wall, and then further reduced by reducing the porosity of the outer porous wall.

[0497] Figure 10d shows the corresponding results for oxygen crossover. Changing the path angle to 50° at the outer porous wall increases oxygen crossover, which is believed to be caused by the flow bias toward the inner porous wall as described above. However, the increase in oxygen crossover is small compared to the reduction in hydrogen crossover, which may be related to the buoyancy-driven flow at the outer porous wall, which serves to limit oxygen crossover. Note that a path angle of 50° brings the angle of the porous region closer to the longitudinal direction. Reducing the porosity at the outer porous wall is also believed to increase oxygen crossover.

[0498] By appropriate variation of the flow bias, one can select a porous wall configuration that provides the desired balance of hydrogen and oxygen crossover. In the example of Figures 10a-10d, hydrogen crossover is generally higher, and therefore variations that tend to drive the flow bias toward the inner porous wall, which serves as the cathode, may be desirable. In other configurations, different flow biases may be established or desired depending on the configuration of the flow configuration (e.g., electrolyzer) and which porous walls serve as the anode and cathode, respectively.

[0499] In a parametric study of the effect of channel diameter on flow patterns in a flow configuration (e.g., an electrolytic cell), simulation cases with porous walls having a graded, discontinuous porous structure were defined. In this parametric study, simulation cases with channel diameters ranging from 50 μm to 500 μm were performed while maintaining other parameters, including (i) a fixed porosity of 0.25 in both the inner and outer porous walls, (ii) a channel angle of 70° in both the inner and outer porous walls, and (iii) a microporosity of 0.5 in both the inner and outer porous walls. It is believed that a microporosity of 0.5 can represent a particle size of approximately 5 μm. The results of the parametric study showed that the flow bias between the inner and outer electrodes, as well as the crossover performance, were substantially the same for each channel diameter tested.

[0500] In a parametric study of the effect of the length of the porous wall (and in particular the longitudinal extent of the porous portion of the porous wall), simulation cases corresponding to S3R3-C and S3R4-C as defined in Table 5 above were defined and run, but the length of the porous wall l main Figures 10e and 10f show the results for hydrogen and oxygen crossover, with the same general trends observed, but with slightly higher species crossover in each case.

[0501] In a parametric study of the effect of microporosity, a set of simulations was defined and run with a baseline configuration as defined in Table 6 below, but with the microporosity of the porous region varied between 0.3 and 0.9 in increments of 0.1, and the total porosity of each porous wall varied accordingly.

[0502] [Table 6]

[0503] Plots of hydrogen and oxygen crossover are provided in Figures 10g and 10h. These show the same general trend of decreasing crossover with flow rate, with both hydrogen and oxygen crossover generally increasing with increasing porosity, corresponding to progressively lower flow resistance through each of the porous walls. The particular configuration of this set of simulation results shows that oxygen crossover increases significantly above a porosity of 0.8 and hydrogen crossover decreases, which may indicate a flow bias toward the inner porous wall.

[0504] Figure 11 shows a schematic representation of an exemplary electrolysis installation 10 comprising an electrolytic cell 100. The electrolytic cell comprises a flow configuration as described above with reference to Figure 1, for example, where one or both of the porous walls have a configuration according to any of the first, second and third examples described above with reference to Figures 1b-1d.

[0505] In sequential flow order as shown, the exemplary electrolysis system 10 includes a source 12 of electrolyte liquid, a compressor 14 for compressing (pressurizing) the electrolyte liquid, a heater 16 for heating the electrolyte liquid, an inlet conduit 18 leading to an inlet manifold 20, an electrolytic cell 100, a first discharge manifold 24, and a second discharge manifold 30.

[0506] In this example, the electrolysis facility is for operation at supercritical conditions in the porous walls of the electrolytic cell, with an electrolyte liquid comprising an aqueous electrolyte solution, for example as described above with respect to the operation of the electrolytic cell 100 of FIG. 1a. In this example, the compressor 14 is configured to compress the electrolyte liquid to a pressure of at least 22 MPa, for example, 22 MPa to 27 MPa. Furthermore, the heater 16 is configured to heat the electrolyte liquid to a temperature of the supercritical condition in the porous walls of the electrolytic cell (for example, at least 374°C, for example, 374°C to 550°C or 374°C to 400°C). Heating may also occur within the electrolytic cell, for example, in the porous walls defining the electrodes. The heater 16 may be configured and / or controlled to heat the electrolyte liquid to a temperature within 50°C of the critical temperature of the respective electrolyte liquid, for example, within 30°C of the critical temperature or within 20°C of the critical temperature. It will be appreciated that the temperature of the electrolyte liquid may be a function of both compression by the compressor 14 and heating by the heater, and that the compressor and heater may be configured and / or controlled to have the stated conditions after the electrolyte liquid has passed through both. The compressor and heater may be provided in any order (e.g., reverse to the order shown).

[0507] An inlet conduit 18 conducts heated and pressurized electrolyte liquid to an inlet manifold 20, which supports a temperature sensor 22 for monitoring the temperature of the electrolyte within the inlet manifold, the temperature sensor being coupled to a controller 56 via a connection 23. Although connection 23 is shown separate from temperature sensor 22 in FIG. 11, it will be appreciated that connection 21 may be any suitable form of connection, for example a wired or wireless link.

[0508] An inlet manifold 20 is coupled to the electrolytic cell 100 to provide electrolyte liquid within the electrolytic cell 100 for the electrolysis reaction as described above with respect to the operation of the exemplary electrolytic cell 100 of FIG. 1a. There are separate first and second outlet passages 23 and 29 (the first and second outlets are configured to discharge a first and second fluid reaction product, respectively) coupled to the electrolytic cell's first and second outlets 132 and 142 (as best shown in FIG. 1a), respectively. FIG. 11 schematically illustrates the first outlet passage 23 coupled to a centrally located first outlet of the electrolytic cell 100, while the second outlet passage 29 is coupled to a radially outward (e.g., annular) second outlet of the electrolytic cell 100.

[0509] The first outlet passage 23 is in fluid communication with a first discharge manifold 24, which receives the flow of electrolyte solution and first reaction product from a first outlet of the electrolytic cell 100. The first discharge manifold 24 is fluidly coupled via a discharge line 25 to a first discharge valve 34. The first discharge valve 34 may be a control valve that provides a variable restriction to the flow therethrough.

[0510] The second outlet passage 29 is in fluid communication with the second discharge manifold 30. As shown schematically in Figure 11, in this example, the first outlet passage 23 extends through the second discharge manifold 30 while functionally bypassing the second discharge manifold (i.e., so that the flow in the first outlet passage 23 does not mix with the flow in the second discharge manifold 30), although this may be configured differently in other embodiments. Like the first discharge manifold 24, the second discharge manifold 30 is fluidly coupled via a discharge line 31 to a second discharge valve 46, which may be of a type similar to the first discharge valve 34.

[0511] Optionally, each of the first and second discharge manifolds 24, 30 is provided with a respective pressure sensor 26, 32 having a pressure sensor element in communication with fluid in a respective chamber discharged from or immediately upstream of a respective (first or second) outlet of the electrolytic cell. Each pressure sensor 26, 32 is coupled to a controller 56 via a respective connection 27, 33 to provide a respective pressure signal to the controller 56 (as noted above, although connections 27, 33 are shown in the drawings as separate from the respective pressure sensors 26, 32, any suitable form of connection may be provided). Alternatively or additionally, a differential pressure sensor may be provided in communication with the respective discharge manifold or outlet passage and connected to the controller 56 to provide a differential pressure signal to the controller 56.

[0512] The first and / or second discharge valves 34 and 46 may be control valves. For example, the first and / or second discharge valves 34 and 46 may be controllable pressure-maintaining valves configured to maintain a target pressure upstream of the respective valves corresponding to target operating conditions within the electrolytic cell 100 (e.g., supercritical electrolyte liquid pressure conditions in the respective porous walls and / or throughout the inlet and outlet chambers of the electrolytic cell). The first and / or second discharge valves 34 and 46 may expand the flow to a lower pressure, e.g., a pressure at which the respective reaction products are gaseous and the residual electrolyte liquid is liquid, so that the respective reaction products can be more easily separated from the electrolyte liquid (e.g., by phase separation in an accumulation tank). The residual electrolyte liquid can be recycled to the electrolyte liquid source 12.

[0513] Optionally, the electrolysis system includes separators 36, 48 downstream of the respective discharge valves 34, 46 for separating the respective fluid reaction products from the electrolyte liquid. Each separator 36, 48 has a respective return line 38, 50 for the flow of discharged electrolyte liquid from the separator that can be returned to the source of electrolyte liquid for reuse. Each separator 36, 48 further includes an outlet line 40, 52 for discharging the respective fluid reaction products. The fluid reaction products may be in gaseous form within the respective separator and may be discharged as gases through the outlet line. Optionally, the monitoring device includes flow meters 42, 54 on the respective outlet lines for monitoring the flow rate of the respective fluid reaction products, each outputting a respective signal to a controller 56, as described below.

[0514] 11, there is a controller 56 coupled to the flow control devices and monitoring devices to control the operation of the electrolytic cell installation 10. The monitoring devices may include a temperature sensor 22 for monitoring the inlet temperature of the electrolyte liquid, pressure sensors 26, 32 (or differential pressure sensors) for monitoring the pressure of the fluids in or discharged from the first and second outlets of the electrolytic cell 100, respectively, and flow meters 42, 54 on the outlet lines 40, 52 for monitoring the outlet flow of the reaction products. The flow control devices may include the monitoring devices.

[0515] The flow control device includes one or more components that determine (i.e., influence or affect) the conditions within the electrolytic cell, such as the thermodynamic and / or flow rate conditions within the electrolytic cell. Thus, the flow control device (or device) may include the heater 16, the compressor 14, the first and second discharge valves 34 and 46, and a cell controller configured to control the current through and / or voltage applied between the first and second electrodes. The controller 56 may include the cell controller.

[0516] The thermodynamic conditions relate to the pressure and temperature of the fluids within the electrolytic cell, for example, the pressure and temperature of the electrolyte liquid provided to the electrolytic cell or the pressure and temperature of the electrolyte liquid combined with the first and / or second reaction products in the respective chambers in which they are held within the electrolytic cell. In this example, the thermodynamic conditions are a function of the pressure to which the electrolyte liquid is compressed in the compressor 14, the temperature to which the electrolyte liquid is heated in the heater 16, any heating of the electrolyte liquid at the porous walls of the electrolytic cell (e.g., as controlled by the cell controller), and, optionally, the operation of the first and second discharge valves 34 and 46 (e.g., the target backpressure that the valves are configured to maintain upstream of the valves).

[0517] The flow rate conditions relate to the flow rate of the electrolyte liquid provided to the electrolytic cell and, optionally, the or each flow rate of a branch stream of electrolyte liquid passing from the inlet chamber through the respective porous wall to the or each outlet chamber.

[0518] At steady-state conditions, the flow rate into the electrolytic cell is equivalent to the sum of the first and second flow rates out of the respective first and second outlets. Each outlet flow may depend on the pressure difference between the inlet chamber of the electrolytic cell and each of the first and second discharge valves 34, 46 (e.g., the pressure at which the compressor 14 compresses the electrolyte liquid), as well as any flow resistance along the respective flow path (e.g., primarily any associated porous walls, but also any other features of the flow path that may cause a pressure drop, such as bends and flow restriction).

[0519] An exemplary method of controlling the electrolysis reaction is described below, by way of example only, with reference to the electrolysis system 10 of FIG. 11 and with reference to the flow diagram of FIG.

[0520] FIG. 12 is a flow diagram of a method for controlling the or each discharge valve 34, 46 associated with an outlet stream containing a mixture of a first fluid reaction product and electrolyte liquid and a mixture of a second fluid reaction product and electrolyte liquid, respectively.

[0521] Block 1202 represents monitoring data received at controller 56 from associated sensors of monitoring devices.

[0522] At block 1204, monitoring data is received at the controller from the associated sensors of the monitoring devices. For example, the data may be received continuously, periodically, on demand, or at the initiative of the respective sensors (e.g., when the sensors detect a predetermined condition).

[0523] In block 1206, the controller evaluates goal criteria related to the monitored data.

[0524] In block 1208, the controller determines settings for one or more of the discharge valves 34, 46 to control operation of the electrolysis equipment based on the evaluation of the target criteria in block 1206. The method continually repeats by returning to block 1204.

[0525] In a first example of method 1200, the monitoring data is upstream pressure data received from pressure sensors 26, 32 configured to monitor the pressure of fluid discharged from each of the first and second outlets of the electrolytic cell (i.e., the outlets of each chamber of the electrolytic cell) or from a pressure differential sensor.

[0526] Evaluating the target criteria may include determining the difference between the pressure of the fluid released through the first outlet 132 (e.g., associated with the first outlet chamber 130) and the pressure of the fluid released through the second outlet 142 (e.g., associated with the second outlet chamber 140), or comparing the pressure of the fluid released from each outlet to a target range of fluid pressures.

[0527] In block 1208, settings for one or more of the release valves may be determined based on an evaluation of the target criteria. For example, there may be a predetermined target range for the pressure difference, and settings may be determined to maintain or return the pressure difference to the target range. When the electrolyzer is operated with no pressure difference between the outlets, the target range may include zero pressure difference. When the electrolyzer is operated with a pressure difference between the outlets, the target range may not include zero pressure difference. The target range (or the respective target range for each pressure) may be predetermined, for example, based on operation of the electrolysis equipment to determine a pressure difference that corresponds to satisfactory performance of the electrolysis equipment with an appropriate balance of flow rates between the outlets. Thus, maintaining the pressure or pressure difference within the respective target range may result in maintaining a target flow rate ratio between the flow from the first outlet and the flow from the second outlet.

[0528] In a second example of method 1200, the monitoring data may be flow rate data, for example, as received from a flow meter configured to monitor the flow rate of the mixture of fluid reaction product and electrolyte liquid streams discharged from the respective outlets 132, 142 of the electrolytic cells (whether upstream of the respective discharge valves 34, 46 or downstream of the respective discharge valves, such as along the respective discharge lines 25, 31). The flow rate data may be received from a flow meter configured to monitor the component flow rates of the respective fluid reaction products being separated from the electrolyte liquid, for example, from a flow meter 42, 54 located on the outlet line for discharging the respective fluid reaction products from the separators 36, 48 downstream of the discharge valves 34, 46.

[0529] The target criteria may correspond to maintaining a target flow rate out of one or each of the outlets or maintaining a target flow rate ratio between the flow out of the first outlet and the flow out of the second outlet. Evaluating the target criteria may include comparing the associated flow rate data to a predetermined target or determining a ratio of the respective flow rates out of the outlets. The controller can determine control settings for one or both valves to maintain the flow rate or flow rate ratio within a target range.

[0530] In a third example of method 1200, the monitored data may be compositional data relating to the composition of the fluid mixture exiting each outlet. For example, the compositional data may be determined by comparing the flow rates of the component fluid reaction products exiting the separator to the total flow rate of the fluids exiting each outlet, e.g., to determine the mass fraction or mole fraction of each fluid reaction product in the fluid mixture exiting each chamber of the electrolytic cell. Alternatively, the compositional data may be determined as the flow rate of each fluid reaction product, regardless of the flow rate at which the electrolyte liquid is exiting each outlet.

[0531] The target criteria may correspond to maintaining a target composition out of each outlet, e.g., a target mass or mole fraction of a fluid reaction product, or a target flow rate, that may be considered to correspond to satisfactory performance of the electrolytic cell. The controller can determine the setting of each release valve based on the composition data. For example, if the mass or mole fraction of a reaction product is determined to be below a target range, this may correspond to too much electrolyte liquid flowing through the respective chamber. Thus, the controller can determine to adjust the setting of the release valve to further restrict flow through the release valve, thereby increasing the mass or mole fraction of the respective fluid reaction product.

[0532] Alternatively, the target criteria may correspond to maintaining a target ratio of the flow rates of the respective fluid reaction products out of the respective outlets of the electrolytic cell. For example, there may be a target range of ratios that corresponds to satisfactory performance of the electrolytic cell, e.g., by having the flow rate of a first reaction product fall within a target range of desired ratios to the flow rate of a second reaction product. The desired ratios may correspond to sustainable performance of each electrolysis reaction (i.e., each half-reaction is balanced).

[0533] The flow rate as described above may be a mass flow rate. A flow meter may monitor the volumetric flow rate of the fluid, and the flow meter or controller may be provided with information corresponding to the density of the respective fluid for determining a parameter corresponding to the mass flow rate.

[0534] In a fourth example of the method, the monitoring data may be compositional data relating to the amount of contaminant fluid reaction products in the fluid streams exiting the respective outlets of the reaction chambers. For example, as described above, a first fluid reaction product will be retained in a first outlet chamber for release through a first outlet of the electrolytic cell, while a second fluid reaction product will be retained in a second outlet chamber for release through a second outlet of the electrolytic cell. Release of the second fluid reaction product through the first outlet corresponds to the presence of contaminant fluid reaction products in the respective outlet streams, and vice versa. The monitoring data may be received, for example, from a constituent gas sensor configured to monitor the composition of the gas downstream of the respective fluid reaction product separator (e.g., at the location of the respective flow meters 42, 54, as described above). While any suitable sensor may be selected, by way of example only, a thermal conductivity sensor configured to determine the composition of the flow stream based on the amount of energy (e.g., power) being monitored may be used to maintain a temperature probe in the flow stream at a target level. When calibrated based on the respective fluid reaction products (e.g., hydrogen) and contaminant fluid reaction products (e.g., oxygen) expected to be released, e.g., based on the respective specific heat capacities of the fluid reaction products, the sensor, or a controller to which the sensor is coupled, is configured to determine when the flowstream includes a certain amount of the contaminant fluid reaction product. For example, it may be calibrated to indicate that the amount is above a threshold, or it may be configured to estimate or calculate the mass fraction of each fluid reaction product (e.g., hydrogen and oxygen).

[0535] The presence of contaminant fluid reaction products may indicate a flow bias toward the respective chamber of the electrolytic cell from which the outlet stream containing the contaminant fluid reaction products is released. Accordingly, the controller may decide to adjust the settings of one or more of the release valves to reduce or control the bias. For example, if an excessive amount of contaminant fluid reaction products is determined in the outlet stream associated with the first release valve 34, the controller may control the first release valve 34 to reduce the flow rate through the first release valve 34 (e.g., by partially closing the valve or setting it to maintain a higher backpressure).

[0536] Although the above examples discuss reactive control methods for maintaining target operating parameters of the electrolyzer, such control methods may be optional and the electrolyzer may be configured to allow the electrolysis reaction to proceed without such intervention. Example Electrolytic Cell and Test 1 The test electrolysis setup, including a source of electrolyte solution 12, a compressor 14, a heater 16, an inlet conduit 18 to an inlet / monitoring manifold 20, an electrolytic cell 100, a first discharge manifold 24, and a second discharge manifold 30, was configured as shown schematically in FIG.

[0537] The electrolytic cell 100 was constructed in the form of a ring-shaped electrolytic cell as shown schematically in Figure 1a. The first (inner) porous wall 110 and the second (outer) porous wall 120 were each connected to a power supply that was biased so that the first (inner) porous wall 110 acted as the cathode and the second (outer) porous wall 120 acted as the anode.

[0538] The first porous wall was created by laser drilling channels into a first tube formed from Inconel® alloy 625 (a nickel-chromium alloy containing iron, molybdenum, niobium, and other alloying elements). The first tube had an outer diameter of 0.25 in. (6.35 mm), a tube wall thickness of 0.889 mm, and a longitudinal length of 215 mm. Prior to laser drilling, the exterior and interior surfaces of the first tube were passivated by coating them with alumina (Al2O3) by chemical vapor deposition (CVD). The alumina coating was approximately 1 μm thick, as determined by gravimetric estimation. The channels were drilled through the entire thickness of the first tube wall (including the alumina coating) using a millisecond laser operating at 500 Hz. When the longitudinal axis of the tube was aligned vertically, the channels were tilted 20° relative to the horizontal (i.e., 70° from the longitudinal axis). Channels were drilled in multiple rows to form the pattern shown in Figure 13. The pattern was characterized by a 0.2 mm channel-to-channel offset, a 0.2 mm row-to-row offset (resulting in five rows per mm), and a circumferential channel number density of 99 holes per circumference of the tube. Each channel was formed using 30 laser pulses, requiring 0.2 J of energy. Channel dimensions were assessed using X-ray computed tomography (XCT) and optical microscopy and analysis of the resulting images. The results are shown in Figures 14, 15(a), and 15(b). The channels were found to have diameters of approximately 60 μm to approximately 80 μm at the channel inlet and outlet (i.e., the outer and inner exterior surfaces of the tube). Figure 15(a) shows a channel found to have an internal radius of approximately 40 μm using XCT. FIG. 15(b) shows channels that were found by optical microscopy to have entrance diameters of about 69.6 μm, about 74.6 μm, and about 65.4 μm.

[0539] The second porous wall 120 was created by laser drilling channels into a second tube formed from Inconel® alloy 625. The second tube had an outer diameter of 0.375 inches (9.525 mm), a tube wall thickness of 0.889 mm, and a longitudinal length of 142 mm. Prior to laser drilling, the exterior and interior surfaces of the second tube were passivated by coating them with alumina (Al2O3) by chemical vapor deposition (CVD). The alumina coating was approximately 1 μm thick, as determined by gravimetric estimation. The channels were drilled through the entire thickness of the second tube wall (including the alumina coating) using a millisecond laser operating at 500 Hz. The channels were tilted 20° relative to the horizontal (i.e., 70° relative to the longitudinal direction) when the longitudinal axis of the tube was aligned vertically. The channels were drilled in multiple rows to form the pattern shown in FIG. 13. The pattern was characterized by a 0.152 mm channel-to-channel offset, a 0.2 mm row-to-row offset (resulting in five rows per mm), and a circumferential channel number density of 196 holes per circumference of the tube. Each channel was formed using 20 laser pulses, requiring 0.18 J of energy. Channel dimensions were assessed using XCT and optical microscopy and analysis of the resulting images. The channels were found to have diameters of approximately 60 μm to approximately 80 μm at the channel inlets and outlets (i.e., the inner and outer surfaces of the tube).

[0540] The first porous wall 110 and the second porous wall 120 were arranged with a separation gap of approximately 0.692 mm, as shown in Figure 1a. The first and second walls were surrounded by an outer tubular housing having a diameter of 19.05 mm. The first inner outlet chamber 130 was defined as the interior space surrounded by the first porous wall 110. The second outer outlet chamber 140 was defined as the space between the second porous wall 120 and the outer tubular housing. The inlet chamber 102 was defined as the space between the first porous wall 110 and the second porous wall 120. In the assembled configuration, the first and second tubes were positioned so that the effective lengths of the electrodes exposed to the inlet chamber for radial flow and ion transport were equal, approximately 40 mm.

[0541] The electrolytic cell was operated using an electrolyte consisting of a 0.5 molar (1.2 wt%) solution of lithium hydroxide (LiOH) in water, prepared by diluting 98% reagent-grade lithium hydroxide (available from Sigma-Aldrich) with deionized water to obtain the desired concentration.

[0542] The heater and compressor were operated to maintain the system at a pressure of 230 bar (23 MPa) and a temperature of 385°C.

[0543] The flow rate of the electrolyte through the electrolytic cell was controlled to be 10 ml / min.

[0544] After initial pressurization and heating of the system with deionized water, the electrolyte was pumped through the electrolyzer upon reaching operating pressure and temperature. The electrolyzer cell was monitored until a voltage drop was observed on the power supply, and then the current supplied to the cell was gradually increased until the operating condition of 500 mA at 1.56 V (corresponding to 80% of the lower heating value of hydrogen) was reached. Electrolysis of the electrolyte was then carried out for 15 minutes.

[0545] During electrolysis, gases output from the first and second outlet chambers into the first and second discharge manifolds were collected in corresponding glass containers filled with deionized water (the product gas displaced the water in the containers as it was collected). The gases collected in the glass containers were analyzed by gas chromatography using an Agilent 6890 gas chromatograph (available from Agilent Technologies, Inc., USA) equipped with a Shincarbon ST column (available from Shinwa Kako Co., Ltd., Japan) supplied with argon as the carrier gas. The gases were detected using a thermal conductivity detector built into the Agilent 6890 gas chromatograph. The gas chromatography run was performed isothermally at 35°C. 100 μL of gas sample was injected into the column at a time. Calibration plots were also generated by injecting various amounts of oxygen and hydrogen into the gas chromatograph and analyzing the results.

[0546] Representative gas chromatography results of gases obtained from operation of the electrolyzer are shown in Figures 16 and 17. Figure 16(a) is a representative chromatogram of gases obtained from the cathode (cathode gas), featuring (from left to right) three peaks related to hydrogen, oxygen, and nitrogen content. Figure 16(b) is a representative chromatogram of gases obtained from the anode (anode gas), also featuring (from left to right) three peaks related to hydrogen, oxygen, and nitrogen content. Figure 17(a) is a representative chromatogram of oxygen calibration gas. Figure 17(b) is a representative chromatogram of hydrogen and nitrogen calibration gases.

[0547] The compositions of the cathode and anode gases, as obtained by gas chromatography, are given in Table 7. These results were obtained by averaging measurements over three different injection samples. The corresponding standard deviations of the measurements are also given.

[0548] [Table 7]

[0549] The values ​​in Table 7 have been corrected to account for air intrusion into the gas storage container by quantifying the amount of nitrogen present in each sample and subtracting an equivalent amount of oxygen according to the ratio of nitrogen to oxygen in air. For example, assuming the N2:O2 ratio in air is 3.7, the volume of oxygen in the sample resulting from air contamination can be calculated as the measured volume of nitrogen in the sample divided by 3.7. Test 2 The test electrolysis setup was configured as in Test 1, except that the laser-drilled channels in the first (inner) porous wall 110 and the second (outer) porous wall 120 of the electrolysis cell were filled with porous Ni-based electrocatalytic material prior to use.

[0550] Filling of the first (inner) porous wall 110 was achieved by drawing a vacuum on the inside of the tube, applying nickel-based conductive ink (available from Creative Materials Inc., Massachusetts, USA under product name 116-25) to the outside of the tube, and allowing the vacuum to draw the ink into the channels. Filling of the second (outer) porous wall 120 was achieved by drawing a vacuum on the outside of the tube, forcing nickel-based conductive ink (available from Creative Materials Inc., Massachusetts, USA under product name 116-25) through the inside of the tube, and allowing the vacuum to draw the ink into the channels. In both cases, excess ink was removed using a dry cloth, and the porous wall was then air-dried for 10 minutes and then rinsed with a small amount of IPA. The tube was then thoroughly dried in an oven at 200°C for 2 hours. The binder material was then removed from the ink during a firing step, whereby the material was pyrolyzed at 300°C for 6 hours, leaving only the metallic ink particles. Finally, the particles were partially sintered together using a high temperature heating and cooling cycle with a target temperature of 930°C.

[0551] The electrolytic cell was operated using an electrolyte consisting of a 0.5 molar (1.2 wt%) solution of lithium hydroxide in water, prepared by diluting 98% reagent grade lithium hydroxide (available from Sigma-Aldrich) with deionized water to obtain the desired concentration.

[0552] Two test runs of the electrolyzer were carried out. In the supercritical run of the electrolyzer, the heater and compressor were operated to maintain the inlet electrolyte at a pressure of 230 bar (23 MPa) and a temperature of 385°C, thus achieving supercritical conditions. In the subcritical run of the electrolyzer, the heater and compressor were operated to maintain the inlet electrolyte at a pressure of 228 bar (22.8 MPa) and a temperature of 350-360°C, thus achieving subcritical conditions.

[0553] The electrolyte flow rate through the electrolytic cell was controlled to be 10 ml / min for each test run.

[0554] After initial pressurization and heating of the system with deionized water, the electrolyte was pumped through the electrolytic cell upon reaching operating pressure and temperature. The electrolytic cell was monitored until a voltage drop was observed on the power supply, and then the current supplied to the cell was gradually increased until the operating conditions of 2 A at 1.31-1.37 V (for supercritical test operation) or 3.8 A at 1.6 V (for subcritical test operation) were reached. Electrolysis of the electrolyte was then carried out for 8 hours.

[0555] The gases output from the first and second outlet chambers into the first and second discharge manifolds were collected in corresponding glass containers filled with deionized water (the product gas displaced the water in the containers as it was collected). The gases collected in the glass containers were analyzed by gas chromatography using an Agilent 6890 gas chromatograph equipped with a Shincarbon ST column (available from Shinwa Kako Co., Ltd., Japan) supplied with argon as the carrier gas. The gases were detected using a thermal conductivity detector built into the Agilent 6890 gas chromatograph. The gas chromatography run was performed isothermally at 35°C. 100 μL of gas sample was injected into the column at a time. Calibration plots were also generated by injecting various amounts of oxygen and hydrogen into the gas chromatograph and analyzing the results.

[0556] The compositions of the cathode and anode gases, as obtained by gas chromatography, are given in Table 8. These results were obtained by averaging measurements over three different injected samples.

[0557] [Table 8]

[0558] The values ​​in Table 8 have been corrected to account for air ingress into the gas storage container by quantifying the amount of nitrogen present in each sample and subtracting an equivalent amount of oxygen according to the ratio of nitrogen to oxygen in air. For example, assuming the N2:O2 ratio in air is 3.7, the volume of oxygen in the sample resulting from air contamination can be calculated as the measured volume of nitrogen in the sample divided by 3.7. Further simulation examples Table 9 below defines the simulation settings and results for a set of simulation cases corresponding to exemplary fabricated electrolytic cells and tests, including those described above with reference to Table 7 and FIGS. 13-17.

[0559] The simulations were performed using the flow simulation model described above with reference to FIG. 7 and Table 3, and all geometry and parameter settings for the simulations were identical to those described above unless otherwise specified below.

[0560] The simulation set includes two simulation cases, S5R1-B and S5R2-C. For simulation case S5R1-B, a porous wall is defined having open, inclined channels corresponding to configuration B as described above (e.g., corresponding to the second example in FIG. 1c or the fifth example in FIG. 2b as described above). For simulation case S5R2-C, a porous wall is defined to have a graded, discontinuous porous structure corresponding to configuration C as described above (e.g., corresponding to the third example in FIG. 1d or the sixth example in FIG. 2c as described above).

[0561] As mentioned above, the simulation cases are each defined to simulate conditions of 23 MPa pressure and 400°C reference temperature.

[0562] Each simulation case was defined to simulate a current through the porous wall of 1 A, which was deemed suitable for comparison of the overall flow bias and crossover effects with respect to the experimental examples described above.

[0563] [Table 9]

[0564] The S5R1-B definition corresponds to an exemplary electrolytic cell fabricated and tested as described above with reference to FIGS. 12-16, with experimental test results reported in Table 7.

[0565] The results of simulation case S5R1-B demonstrate that the flow simulation model reflects the flow patterns and results observed by experimental testing. In particular, the flow simulation model appears to simulate flow through the porous walls, and as a result, when the resulting crossover of electrolysis reaction products is compared, they exhibit the same direction of flow bias. The experimental test results show significantly higher hydrogen crossover (57% ± 0.17 molar concentration in the outer outlet gas) compared to oxygen crossover to the inner outlet (1.54% ± 0.94 molar concentration in the inner outlet case). The same trend is reflected in simulation case S5R1-B, where both the simulation and experiment predict hydrogen crossover (mol %) an order of magnitude greater than oxygen crossover. This indicates that the flow patterns modeled by the flow simulation model are representative of those occurring in experimental testing. porosity Three sample porous walls were created by laser drilling channels into three hollow tubes formed from Inconel® ...

Claims

1. 1. A flow configuration for an electrolytic cell comprising: a first porous wall and a second porous wall corresponding to the first electrode and the second electrode of the electrolytic cell; an inlet chamber disposed between the first porous wall and the second porous wall and configured to receive a fluid through an inlet; first and second outlet chambers for retaining respective fluid reaction products of electrolysis, separated from said inlet chamber by said first and second porous walls, respectively; Equipped with One or each of the first porous wall and the second porous wall has a discontinuous porous structure, and the or each porous wall having the discontinuous porous structure comprises: a body having an inlet side adjacent to the inlet chamber and an outlet side adjacent to each of the outlet chambers, the body being elongated along a longitudinal direction and having a thickness direction from the inlet side to the outlet side; a plurality of porous regions extending through the body at discrete locations to allow the fluid to flow from the inlet chamber to respective outlet chambers; A flow configuration in which each porous region defines a respective network of flow channels through the body.

2. 2. The flow configuration of claim 1, wherein for the or each porous wall having the discontinuous porous structure, each porous region is elongate along a path through the body having a longitudinal component.

3. 3. The flow configuration of claim 2, wherein for the or each porous wall having the discontinuous porous structure, each porous region is elongate along a path through the body that defines a path angle with respect to the longitudinal direction of between 20° and 80°.

4. Both the first porous wall and the second porous wall have the discontinuous porous structure, and at least one characteristic of the discontinuous porous structure differs between the first porous wall and the second porous wall by a respective minimum offset, and the characteristic is: the porosity of each said porous wall, with an associated minimum offset of 0.01; the macroporosity of each said porous wall, defined for each porous wall as the porosity of the body of said porous wall in the absence of said porous region, with an associated minimum offset of 0.01; the microporosity of each said porous wall, defined for each porous wall as the porosity of the porous region, with an associated minimum offset of 0.05; the pitch at which each of the porous regions is spaced apart, with a minimum offset of 10% relative to the minimum value of each of the porous walls' pitch; an average cross-sectional area of ​​each of the porous regions, each cross-sectional area being determined by dividing the volume of the porous region by the extent of the porous region along the thickness direction, with an associated minimum offset of 10%; the average diameter of each porous region when each porous region has a circular cross section perpendicular to the path along which the porous region extends, with an associated minimum offset of 10%; a path angle of each porous region, determined as the angle between the path along which the porous region extends and each longitudinal direction, with an associated minimum offset of 5°; and The thickness of the porous wall along each of the thickness directions, with an associated minimum offset of 10% for the thinnest porous wall. The flow configuration of any one of claims 1 to 3, selected from the group consisting of:

5. For the or each porous wall having the discontinuous porous structure, A flow arrangement according to any one of claims 1 to 4, wherein each of the porous regions has a porosity of between 0.2 and 0.

9.

6. For the or each porous wall having the discontinuous porous structure, Each porous region has a thickness of 10,000 to 250,000 μm ２ each cross-sectional area being determined as the volume of the porous region divided by the extent of the porous region along the thickness direction; and / or A flow arrangement according to any one of claims 1 to 5, wherein each porous region has an average diameter of 25 to 250 μm.

7. For the or each porous wall having the discontinuous porous structure, A flow arrangement according to any one of claims 1 to 6, wherein the material composition of the porous region is different from the material composition of the body.

8. For the or each porous wall having the discontinuous porous structure, the body is integrally formed with the plurality of porous regions; 7. The flow configuration of claim 1, wherein each porous region surrounds the porous region and interfaces with the body at a respective boundary defined by a change in porosity between the body and the porous region.

9. For the or each porous wall having the discontinuous porous structure, The flow arrangement of claim 8 , wherein the material composition of the body is the same as the material composition of each of the porous regions.

10. 10. An electrolytic cell for carrying out continuous electrolysis of an electrolyte liquid, the electrolytic cell comprising a flow arrangement according to any one of claims 1 to 9 for receiving electrolyte liquid at an inlet, the first and second porous walls providing first and second electrodes of the cell respectively.

11. 11. The electrolytic cell of claim 10, further comprising a controller configured to control a flow control device to maintain a supercritical condition of the electrolyte solution in the first porous wall and / or the second porous wall.

12. 12. The electrolytic cell according to claim 11 , wherein the controller is configured to control flow control devices to maintain supercritical pressure and temperature conditions of the electrolyte liquid in the first porous wall and / or the second porous wall of a pressure of at least 22 MPa and a temperature of at least 374° C. for aqueous electrolyte liquid.

13. For the or each porous wall having said discontinuous porous structure and providing an electrode of said electrolytic cell:

13. An electrolytic cell according to any one of claims 10 to 12, wherein the porous regions contain an electrocatalyst and thereby define an electrocatalytic area of ​​each of the electrodes for an electrolytic half-reaction.

14. For the or each porous wall having said discontinuous porous structure and providing an electrode of said electrolytic cell:

14. The electrolytic cell of claim 13, wherein each of the respective porous regions comprises a porous medium formed from electrocatalyst-containing particulates.

15. For the or each porous wall having the discontinuous porous structure, the material composition of the porous region is different from the material composition of the body; Optionally, the body comprises a passive area for each of the electrodes to suppress electrolysis.

16. For the or each porous wall having the discontinuous porous structure, the body is integrally formed with the plurality of porous regions; each porous region surrounds the porous region and interfaces with the body at a respective boundary defined by a change in porosity between the body and the porous region; the porous region contains an electrocatalyst and thus belongs to the electrocatalytic region of each of the electrodes for an electrolytic half-reaction; Electrolyzer according to any one of claims 10 to 14, wherein the porous region and the body have a common material composition that includes the electrocatalyst.

17. For the or each porous wall having the discontinuous porous structure, the inlet side of the body is defined by a passive region configured to be less electrocatalytically active than the electrocatalytic region; Optionally, the passive area comprises a passivation coating defining the inlet side of the body for suppressing electrolysis.

18. a source of electrolyte solution, optionally an aqueous electrolyte solution; an electrolytic cell according to any one of claims 10 to 17 for carrying out continuous electrolysis of the electrolyte solution; Electrolysis equipment.

19. A method for operating an electrolytic cell according to any one of claims 10 to 17 or an electrolytic installation according to claim 18, comprising the steps of: providing an inlet flow of electrolyte liquid to the inlet chamber via the inlet for carrying out electrolytic half-reactions at first and second electrodes provided by the first and second porous walls to produce respective fluid reaction products; the electrolyte solution and / or associated ions flow into the porous region of the or each electrode having a discontinuous porous structure and react with the respective electrode; The method, wherein each of the first and second outlet chambers holds a respective one of the fluid reaction products for release, and each of the electrodes inhibits return flow of the fluid reaction products from the outlet chamber to the inlet chamber.

20. 20. The method of claim 19, further comprising controlling thermodynamic and / or flow rate conditions to maintain supercritical temperature and pressure conditions of the electrolyte liquid in the first porous wall and / or the second porous wall.

21. 1. A method for producing a porous wall having a discontinuous porous structure of an electrolytic cell, comprising the steps of: providing a body of the porous wall, the body being elongate along a longitudinal direction and having a thickness direction from a first side to a second side; removing material from the body to form a plurality of open areas, the open areas extending through the body at discrete locations, each open area being elongate along a path through the body having a longitudinal component; depositing an electrocatalyst composition on the body such that the electrocatalyst composition flows into the open area; heating the body to perform a heat treatment operation in which the electrocatalytic component of the electrocatalyst composition forms porous regions at each location of the open regions, each porous region defining a respective network of flow paths through the body for permitting fluid to flow from the first side of the body to the second side of the body; A method comprising:

22. 22. The method of claim 21, further comprising a drying operation to evaporate components of the electrocatalyst composition, performed after depositing the electrocatalyst composition and before the heat treating operation.

23. The method of any one of claims 21 to 22, wherein the heat treatment operation comprises heating the body to a target temperature of 150 to 1000°C.

24. 24. The method of any one of claims 21 to 23, wherein the electrocatalyst composition has a viscosity of about 1 Pa·s to about 30 Pa·s when applied to the body.

25. The method of any one of claims 21 to 24, wherein the electrocatalyst composition, when applied to the body, comprises a mixture of an electrocatalyst and a liquid.

26. A method according to any one of claims 21 to 25 for providing a porous wall having a discontinuous porous structure of a flow arrangement according to any one of claims 1 to 7 or an electrolytic cell according to any one of claims 10 to 15.

27. 1. A method for producing a porous wall having a discontinuous porous structure of an electrolytic cell, comprising the steps of: forming a porous wall by an additive manufacturing process, the porous wall comprising: a body having a first side and a second side, the body being elongate along a longitudinal direction and having a thickness direction from the first side to the second side; a plurality of porous regions extending through the body at discrete locations to allow fluid to flow from the first side to the second side; each porous region defining a respective network of flow channels through said body; each porous region is elongate along a path through the body having a longitudinal component; A method wherein the additive manufacturing process is controlled to vary the porosity of the porous walls during formation such that the porous region is formed with a higher open porosity than the body.

28. 28. The method of claim 27, wherein the porous region and the body have a common material composition that includes the electrocatalyst.

29. 29. The method of claim 27 or 28, further comprising providing a passivation coating on the first side of the body configured to be less electrocatalytically active than an electrocatalytic area of ​​the porous wall that includes the porous region.

30. A method according to any one of claims 26 to 29 for providing a porous wall having a discontinuous porous structure of a flow arrangement according to any one of claims 8 to 9 or an electrolytic cell according to claim 16 or 17.

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