Composite sintered body

Abstract

An electrode assembly for REM electrolysis, comprising a porous sintered plate, a first mesh layer having an expanded metal mesh and an inner surface bonded to the surface of the porous sintered plate, and a protective coating applied to the assembly, wherein the first mesh layer is bonded to the porous sintered plate at a plurality of point contact regions.

Description

Technical Field

[0001] The present invention relates to an electrode assembly for polymer electrolyte membrane (PEM) electrolysis.

Background Art

[0002] The hydrogen industry is widely expected to be an important part of the drive towards decarbonization and a net-zero emissions economy. Hydrogen can combine with oxygen and release energy for electricity by directly burning hydrogen or by generating electricity in a fuel cell. In either case, water is produced as a by-product. Hydrogen also has industrial applications, for example, in the manufacture of steel and glass and as a component of many chemical processes. Hydrogen power has the advantage of using proven technology (hydrogen fuel cells were used as far back as the Apollo missions) and not generating greenhouse gases.

[0003] Although hydrogen is the most abundant element in the universe, it is not generally found in commercial quantities on Earth and must be produced. Hydrogen can be produced using PEM (proton exchange membrane) electrolysis. This method is essentially the reverse of a fuel cell. Water passes through charged PEM electrodes, which separate the water into hydrogen and oxygen. Unlike other hydrogen production methods, PEM electrolysis does not produce carbon dioxide or greenhouse gases as by-products. The membrane is impermeable to gases, ensuring safety and enabling the gas produced at each electrode to self-pressurize. However, this requires a precisely tuned electrode / membrane interface. Furthermore, PEM electrolysis can be powered by renewable energy sources such as wind turbines. As a result, PEM electrolysis can be used to produce hydrogen with very low carbon emissions.

[0004] PEM electrolysis is typically carried out by passing water through an electrochemical cell and applying a direct current (DC) voltage to two electrodes separated by a gas-impermeable proton exchange membrane: a negatively charged cathode and a positively charged anode. At the anode, the water is oxidized, giving protons and oxygen. The protons then move through the proton exchange membrane and are subsequently reduced by electrons at the cathode to produce hydrogen. The protons (positively charged hydrogen ions) then move through an ion transport membrane (solid polymer electrolyte - PEM) to the cathode, where they combine with electrons to form molecular hydrogen. The molecular hydrogen in gaseous form can then be collected under pressure.

[0005] However, existing systems and methods for PEM electrolysis have drawbacks. Existing PEM electrolysis assemblies are generally complex multiphase fluid systems, often prone to corrosion, and expensive to manufacture and install. Many of these drawbacks represent potential efficiency losses within the system, which can increase the amount of electricity required to produce hydrogen units. Therefore, there is a need for a PEM electrolysis system that increases efficiency and reduces overall costs. [Overview of the Initiative]

[0006] According to a first aspect of the present invention, an electrode assembly for PEM electrolysis is included, the electrode assembly comprising a porous sintered plate, a first mesh layer comprising an expanded metal mesh having an inner surface bonded to the surface of the porous sintered plate, and a protective coating applied to the assembly, the first mesh layer being bonded to the porous sintered plate at a plurality of point contact areas.

[0007] Preferably, the assembly comprises two mesh layers, each having an expanded metal mesh, the second mesh layer having an inner surface joined to the outer surface of the first mesh layer at a plurality of point contact areas.

[0008] Preferably, the first mesh layer and the second mesh layer each include one or more vertices and a plurality of point contact regions. Preferably, the plurality of point contact regions are located at the vertices on the surface of each mesh layer.

[0009] Preferably, each of the first mesh layer and the second mesh layer has a soft apex surface and a hard apex surface, the apex of the soft apex surface being softer than the apex of the hard apex surface, and the first mesh layer and the second mesh layer are joined together such that the soft apex surface of the second mesh layer faces outward.

[0010] Preferably, at least one mesh layer comprises a mesh structure formed by a plurality of strands, and a plurality of diamond-shaped holes defined by the mesh structure, wherein the diamond-shaped holes have an acute angle of 53 to 58 degrees at the joints between the strands.

[0011] Preferably, the point contact area is located along the edge of the hole, defined by the mesh structure of the first mesh layer.

[0012] Preferably, the first mesh layer includes a mesh structure formed by a plurality of strands, and the strands of the first mesh layer have an average thickness of 0.3 to 0.6 mm.

[0013] Preferably, at least one of the mesh layers has an open volume of 60% to 80% and a minimum front opening area of ​​35%.

[0014] Preferably, each of the first and second mesh layers comprises a mesh structure, the mesh structure including a plurality of holes, and when assembled, the plurality of holes in the mesh structure of the first mesh layer extend in a first direction, and the plurality of holes in the mesh structure of the second mesh layer extend in a second direction. Preferably, the first direction and the second direction are orthogonal to each other.

[0015] Preferably, the flatness of the uppermost and lowermost surfaces of the electrode assembly is 0.01 to 0.03 mm per meter.

[0016] Preferably, the first mesh layer is bonded to the second mesh layer and one of the porous sintered plates with a bonding coverage of 15% or more of the area of ​​the electrode assembly.

[0017] Preferably, the electrode assembly further comprises a third metal mesh layer having an expanded metal mesh and an inner surface bonded to the surface of a porous sintered plate, and a fourth mesh layer having an expanded metal mesh and an inner surface bonded to the outer surface of the third mesh layer. Preferably, the third and fourth mesh layers are separated from the first and second mesh layers.

[0018] Preferably, the porous sintered plate and at least one of the one or more mesh layers contain titanium.

[0019] Preferably, the protective coating contains platinum or a mixture of precious metal oxides.

[0020] Preferably, the porous sintered plate includes multiple porous networks.

[0021] Preferably, the porous sintered plate includes a microporous coating formed from at least two different grades of sintered powder.

[0022] Preferably, at least one of the one or more mesh layers has at least one channel on its surface.

[0023] Preferably, the flow path has a nonlinear shape.

[0024] Preferably, each of at least one channel is a microfluidic channel with a diameter of less than 750 μm perpendicular to the flow direction.

[0025] Preferably, the electrode assembly has an active area of 1000 to 2100 square centimeters.

[0026] Preferably, the electrode assembly has a thickness of 1.1 to 2.8 mm.

[0027] According to a second aspect of the present invention, a method for manufacturing an electrode assembly for PEM electrolysis, the method comprising joining an inner surface of a first expanded metal mesh layer to a surface of a porous sintered plate, and applying a protective coating to the electrode assembly, wherein the first mesh layer is joined to the porous sintered plate at a plurality of point contact regions.

[0028] Preferably, the method further comprises joining a second expanded metal mesh layer to an outer surface of the first mesh layer, and the first mesh layer is joined to the second expanded metal mesh layer at a plurality of point contact regions.

[0029] Preferably, after joining the first expanded metal mesh layer to the surface of the porous sintered plate, the second expanded metal mesh layer is joined to the outer surface of the first mesh layer.

[0030] Preferably, projection welding is used for joining the first mesh layer to the porous sintered plate and for joining the first mesh layer to the second mesh layer.

Brief Description of the Drawings

[0031] [Figure 1a] Shows a schematic view of the assembly. Figure 1a is an exploded view, and Figure 1b is also a plan view including the positioning position of the welding head. [Figure 1b] Shows a schematic view of the assembly. Figure 1a is an exploded view, and Figure 1b is also a plan view including the positioning position of the welding head. [Figure 2a] Each shows a portion of the soft vertex surface and the hard vertex surface of the mesh for use in the assembly. [Figure 2b]These show the soft vertex faces and hard vertex faces of the mesh, respectively, for use in assembly. [Figure 3] An overlaid mesh layer is shown according to one embodiment of the present invention. [Figure 4] This figure shows the point contact areas between mesh layers within the assembly. [Figure 5] This shows some of the components of the assembly, including the flow channels. [Figure 6a] A schematic diagram of the assembly is shown. Figure 6a is an exploded view, Figure 6b is a plan view, and Figure 6c is a cross-sectional view of Figure 6b along line AA. [Figure 6b] A schematic diagram of the assembly is shown. Figure 6a is an exploded view, Figure 6b is a plan view, and Figure 6c is a cross-sectional view of Figure 6b along line AA. [Figure 6c] A schematic diagram of the assembly is shown. Figure 6a is an exploded view, Figure 6b is a plan view, and Figure 6c is a cross-sectional view of Figure 6b along line AA. [Figure 7] This is a schematic exploded view of the assembly, including the central gap. [Modes for carrying out the invention]

[0032] Referring to Figure 1, an exemplary assembly 100 includes a porous sintered plate 101, a first mesh layer 102 (also known as an inner mesh layer) 102, and a second mesh layer 103 (also known as an outer mesh layer). In an alternative embodiment, assembly 100 may comprise the sintered plate 101 and the first mesh layer 102, but without the second mesh layer 103. A single mesh layer 102 can direct fluid flow and conduct electric current, as described below, but two or more mesh layers are more effective. The porous sintered plate 101 comprises a sintered titanium powder material having open-cell porosity and may include multiple porous meshes having different characteristic diameters, i.e., large, medium, and small diameters. These different-sized porous meshes provide different types of transport mechanisms through the porous sintered plate 101. For example, small-diameter porous meshes enable capillary transport, while large-diameter porous meshes enable osmotic transport. Porous meshes can support different substances depending on their size. For example, in an anode electrode, oxygen can be transported towards the PEM membrane by osmosis through large-diameter porous meshes, while water can be carried away from the PEM membrane by capillary action through small-diameter porous meshes. The shape of the pores can be either spherical or random and can be fully characterized by those skilled in the art. Apart from physical attributes, geometric attributes such as length, width, and flatness can also be strictly controlled in the raw materials.

[0033] When assembled, the porous sintered plate 101 and the mesh layers 102, 103 are in electrically non-wet contact with each other and can be used to direct fluid flow and conduct electric current. The mesh layers 102, 103 are mostly open space (ranging from 60% to 80%, with at least 35% of the front opening area) and provide sufficient structural strength and rigidity without obstructing fluid flow, while also providing sufficient flow resistance to distribute fluid well within the cell. The “expanded metal mesh” as used in this disclosure may refer to a metal sheet or foil that has been sheared without material loss and then stretched to form a mesh. However, other forms of mesh, such as a mesh made of woven metal wire, may also be used. The outer surface of the porous sintered plate 101 (i.e., the side not joined to the inner mesh layer 102) is pressed against a catalyst layer (not shown), which itself covers a PEM film (not shown). The electrolytic reaction occurs at the interface between the porous sintered plate 101 and the catalyst layer.

[0034] A porous sintered plate 101 containing multiple porous networks can be manufactured by combining powders containing particles of different sizes and compressing them to form a sintered body. In one example, the powder used has a particle size in the range of 30 microns to 210 microns. Since particles of different sizes do not tile in a regular arrangement, when nested together they create multiple voids of different sizes. These voids are interconnected and provide transport conduits through the porous sintered plate 101.

[0035] The porous sintered plate 101 may include a microporous coating formed from at least two different grades of sintered powder. The purpose is to increase the density of contact points with the PEM film and maximize the continuous contact area. The powder grade refers to its coarseness or fineness. Powder grades can be classified by the smallest nominal mesh opening size through which the powder can be sieved. In other words, the powder grade may indicate the upper limit of particle diameter in the powder.

[0036] Mesh layers 102 and 103 are formed of expanded metal mesh, each comprising a plurality of holes 104. The holes 104 may be elongated and diamond-shaped / rhomboid, as shown. Diamond-shaped holes, due to their different permeability coefficients in two directions, promote biaxial flow separation, or polarization, of water as it flows through the mesh layer, helping to mix the water and direct it to all areas of the electrode assembly. Two layers of the same mesh provide greater flow with less pressure drop. For clarity, the mesh layers 102 and 103 in Figures 1, 6, and 7 are shown as flat sheets with relatively small holes 104. However, in practice, the mesh layers 102 and 103 may have larger holes 104, such that the mesh layers 102 and 103 are mostly empty space. Similarly, the surfaces of the mesh layers 102 and 103 may be undulating, rather than flat, as shown, and may have peaks and valleys. The inner mesh layer 102 may have elongated holes 104 that are elongated in a direction perpendicular to the elongation of the holes in the outer mesh 103, as shown. This arrangement ensures that the mesh layers 102 and 103 interfere with each other rather than nesting together, which ensures that contact between layers occurs only in point contact areas and over relatively small areas. Alternatively, nesting between the mesh layers 102 and 103 can be prevented by using holes of a different size or elongated shape in one mesh layer compared to the other mesh layer, so that the vertices and valleys of the mesh layers 102 and 103 do not align.

[0037] In one embodiment, at least one of the porous sintered plate 101, the inner mesh layer 102, and the outer mesh layer 103 contains titanium. In some examples, the mesh layers 102 and 103 are made of Grade 1 titanium mesh. Other titanium alloys, such as those containing aluminum, tin, molybdenum, vanadium, zirconium, niobium, or chromium, may be suitable or desirable. In some examples, the mesh layers 102 and 103 have an open volume of 60-80% and a minimum front opening area of ​​35%.

[0038] An exemplary method for joining the layers of the assembly is described below with reference to Figure 1b. The porous sintered plate 101 is held in a jig (the porous sintered plate and the jig are not shown). The inner mesh layer 102 is provided on the surface of the porous sintered plate 101 and is positioned precisely within the jig, with the point contact area preferably in full contact with the surface of the porous sintered plate 101. The jig is moved by a robot under a series of rectangular welding heads arranged in a row, so that up to 24 welding heads are aligned in a row, thereby positioning the welding heads over a first subset 104a of welding head positioning positions 104. The welding head positioning positions 104 may be equally spaced, as shown, to generate a regular pattern.

[0039] The point contact regions of mesh layers 102 and 103 are areas of the mesh layer's surface that come into contact with another component. The contact regions are "points" in the sense that they have small widths, lengths, and areas. When a mesh layer is joined to another component using welding, the welding current is concentrated over a small area of ​​the point contact region, which can result in strong but very localized heating. This is called "solid-state welding" because the melting is localized and minimized. The point contact regions can be appropriately sized to concentrate the current at discrete points so as to produce a strong bond in the point contact region without locally collapsing the structure of the mesh layer, which could impair the flatness of the electrode assembly. By minimizing the total contact area on the mesh layer and carefully controlling the welding procedure, power source, and localized contact area in the point contact region, the welding current can be concentrated to minimize the diffusion of molten metal. This can reduce the energy required to join the components.

[0040] In one embodiment, the welding area (i.e., the percentage of the area of ​​the electrode assembly as viewed perpendicular to the plane of the mesh layers 102 and 103, covered by the welding head positioning position 104) is approximately 30% to 40%. In one embodiment, the area of ​​each welding head (i.e., the area enclosed by the contour of each welding head positioning position 104) is 370 mm².2 ~3400mm 2 Ideally, 880mm 2 It should be so. The welding head may be made of hard copper or beryllium copper, with or without a tungsten tip that forms contact with the part.

[0041] Once the fixture is correctly positioned, the welding head moves to contact the outer surface of the inner mesh layer 102 and operates to transmit the welding current. The welding head is operated from the same power source and can be controlled by a welding head control unit. To reduce constraints on the power source and the magnitude of the required current, the welding head control unit may, in some examples, operate the welding head at different times rather than simultaneously. After the welding operation is performed, the fixture is repositioned so that the welding head is positioned over a second subset 104b of the welding head positioning position 104. This process is repeated until a sufficient area of ​​the inner mesh layer 102 is welded to the porous sintered plate 101.

[0042] A typical welding sequence consists of at least one holding cycle and at least one welding cycle. During the holding cycle, the two components to be welded are held together, for example, using clamps. During the welding cycle, a welding current of 50 Hz may be applied between the components. In some examples, the welding intensity during the welding cycle is 340–1360 A / cm². 2 It is possible.

[0043] Following each welding cycle and / or welding sequence, the welded components are cooled for at least one cooling cycle to allow the weld nugget to solidify. Generally, the welding cycles, pressing cycles, and cooling cycles do not overlap. An exemplary welding sequence consists of 4 to 8 holding cycles, 2 to 18 welding cycles interspersed therebetween, and 8 cooling cycles. Each cycle lasts for 20 milliseconds (ms). Typically, 1 to 3 welding sequences are applied at each welding head positioning position 104. Each welding sequence forms a first set of welds in the point contact region with the highest resistance. Since the weld nugget itself acts as a conductor in the point contact region, the resistance in the welded point contact region is reduced by the weld. Therefore, applying a second welding sequence following a first welding sequence may result in the formation of a second set of welds in the point contact region with the highest resistance.

[0044] The welding pattern can be set by using a robot positioner and a welding head control unit in combination. The robot positions the welding head on a subset of welding head positioning positions 104, and the welding head control unit then operates the welding head in a specific sequence. In one embodiment, the welding pattern determined by the robot and the welding head operates from the center of gravity of the electrode outwards. In another embodiment, the welding sequence begins on the outside of the electrode and follows a path inwards. The welding pattern and density may differ between the anode and cathode electrodes.

[0045] The procedure detailed above may be repeated to join the outer mesh layer 103 to the inner mesh layer 102. In this case, the welding head is positioned on the outer surface of the outer mesh layer 103, above the welding head positioning position. Joining the parts into a single assembly 100 is advantageous because it speeds up the process of manufacturing larger electrolytic cell devices. Rather than inserting each layer of assembly 100 into the device one by one, the electrode assembly 100 can be handled and inserted in a single step.

[0046] When the porous sintered plate 101 and the mesh layers 102 and 103 are joined together to form assembly 100, a protective coating is applied to assembly 100. The protective layer prevents the naturally occurring titanium oxide layer from growing and impairing the electronic conductivity of the mesh layer. In other words, the protective layer protects the electrodes and adjacent parts from the oxidation conditions of the battery and maintains low resistance for electron transport. This, in turn, extends the lifespan of the device by preventing oxide growth.

[0047] Applying a precious metal protective coating to the assembled electrode 100 may offer cost savings compared to applying protective coatings to the individual components 101-103 before joining. The protective coating can prevent oxide growth on the electrode, which could otherwise interfere with the electrolytic reaction. A further advantage of coating the assembly after joining is that this type of oxide growth typically occurs only on the external surfaces of the assembly that come into contact with water and PEM, and therefore the protective coating is typically applied only to surfaces that would be susceptible to oxidation. If protective coatings are applied to the parts before the assembly is fully assembled, at least some of the coating will be applied to areas covered by the weld nugget or areas trapped between parts at the interface between joined parts. Such areas are typically less susceptible to oxidation even if left uncoated, meaning that any protective coating applied to these areas may be redundant. Furthermore, the energy required to weld surfaces that are already coated with a protective coating may be higher. In some cases where components are coated before joining, the welding current can evaporate part of the coating, wasting both energy and coating material. Applying a precious metal coating to assembled electrodes (after joining) means that the coating is applied only to the exposed surfaces of the assembly, thereby reducing the energy required for welding. The amount of protective coating required can be reduced by approximately 40% by coating the assembly after joining rather than coating the components individually. The protective coating materials according to this disclosure are typically expensive, and therefore even small material savings can be significant.

[0048] The mesh layer is marked with an orientation indicator 105, which may allow an operator or automated system to determine whether the sides of the mesh layer with rigid or soft vertices face the operator or system. For example, the orientation indicator 105 may be a pattern of holes punched into the corners of the faces of the rigid vertices of the mesh, with the faces of the rigid vertices facing the operator. If the mesh is oriented in the opposite direction, with the faces of the soft vertices facing the operator, the pattern of holes may be found at different corners from the operator's viewpoint. This ensures that the mesh layer can be oriented quickly and accurately during assembly, including by an automated assembly machine.

[0049] Figures 2a and 2b show detailed three-dimensional views of the faces of the expanded mesh layer 200. Figure 2a shows face A, and Figure 2b shows face B. The mesh layer 200 is an expanded metal mesh, which can be manufactured by first punching holes 104 into a metal sheet. The sheet is then stretched in a die in the direction indicated by arrow 204 to expand the holes 104 and thin the metal around the holes into thin strands. In some examples, the strand thickness is 0.3–0.6 mm and the strand width is 0.5–0.7 mm. After expansion, the mesh layer is typically 0.88–0.92 mm thick. The holes 104 may be diamond-shaped, stretched such that the length 206 of the hole 104 is greater than its width 207, as shown. In one example, the length 206 is 4 mm and the width 207 is 2.2 mm. In one example, the acute angle α at the joint between strands is 53 to 58 degrees.

[0050] When expanded, the mesh layers 102 and 103 may begin to bend due to the mesh and the coiling of the material. To maintain the flatness of the layers and the entire assembly 100, the acceptable offset due to bending must be controlled. In some examples, when the mesh layers 102 and 103 are placed on a flat surface, the vertical offset between the flat surface and any portion of the bottom surface of the mesh layers 102 and 103 does not exceed a value of 1 to 8 mm. In some examples, the flatness of the outer surface of the outer mesh layer 103 is constrained to 0.01 to 0.04 mm / m in the welded state.

[0051] The flatness of the outer surface of the electrode assembly 100 may be constrained to ensure that the electrodes can be stacked and assembled together with other components. This ensures that multiple electrode assemblies and other components can be stacked together in a straight line within the electrolytic cell without deforming each other or leaving gaps between the outermost surfaces of adjacent electrode assemblies. It is well known to those skilled in the art that constrained flatness (both locally and across the entire electrode) is a necessary prerequisite for good electrochemistry. In other words, the contact between the electrode and the PEM film must be continuous. This is necessary to obtain a homogeneous reaction, good electron transfer, and good ion transfer. Areas of the electrode not in contact with the PEM film, or even areas with insufficient contact pressure, do not contribute to reactions that require a localized supply of current. Insufficient or inconsistent contact not only reduces efficiency but can also cause the current to be redirected through adjacent areas, leading to overload and excessive wear.

[0052] Both sides of the mesh layer 200 may be wavy and may have peaks and valleys, but the indicated peaks 201 on surface A (the soft peak surface) have soft, curved ridges 203, while the indicated peaks 202 on surface B (the hard peak surface) have hard, sharp-edged flat portions 205. These flat portions 205 make the peaks 202 on surface B harder and sharper than the peaks 201 on surface A.

[0053] As mentioned above, in some examples, the expanded metal mesh layer 200 can be manufactured by punching holes 104 into a metal sheet and then stretching the sheet along direction 204 to enlarge the holes. This punching process may leave burrs along the edges of the holes 104 on the side (B side) of the sheet opposite to the punched side (A side). When the punched sheet is expanded to form a mesh, the burrs may be stretched into sharp protrusions 203 along the vertices 201 of side B.

[0054] Figure 3 shows the stacked components of the assembly from above. In the shown assembly, the top is the outer mesh layer 103, and below it is the inner mesh layer 102. A porous sintered plate 101 may be seen at the bottom. The mesh layers 102 and 103 are joined using solid-state resistance welding, which leaves no visible weld nuggets. The elongated lengths of the holes 104 in the inner mesh layer 102 and the outer mesh layer 103 are orthogonal to each other. As shown in Figure 3, the assembly 100 may be arranged such that the holes in the mesh layers 102 and 103 do not form a repeating geometric pattern. This ensures that the inner mesh layer 102 and the outer mesh layer 103 do not nest over each other, and the total contact area between the mesh layers is minimized. Minimizing the total contact area also increases the current density during welding, which means that a lower welding current is required to join the mesh layers 102 and 103.

[0055] Figure 4 shows an example of how the components of the electrode assembly may be arranged. In the illustrated assembly, the inner mesh layer 102 and the outer mesh layer 103 are arranged so that the A-face of the soft vertices faces outward. The vertices 201 of the B-face on each mesh layer 102, 103 include a flat region 205 with a hard, sharp side surface. The inner mesh layer 102 is shown with its B-face as the outer surface, and the mesh layer has an "AB-BA" configuration. Alternatively, the inner mesh layer 103 may be configured so that its A-face is the outer surface, and as a result the mesh layer has an "AB-AB" configuration. The inner surface of the mesh layer 102 is bonded to the porous sintered plate 101.

[0056] In some examples, the outer mesh layer 103 can be stacked on top of the inner mesh layer 102 without nesting (i.e., at a constant height) by ensuring that the vertices of the inner layer 102 do not align with the valleys of the outer mesh layer 103 (and vice versa). In other words, the vertex pitch 402 on the inner mesh layer 102 along a particular direction should be different from the vertex pitch 403 on the outer mesh layer 103 along the same direction. In the plane of Figure 4, the vertex pitch 402 of the inner mesh layer 102 is shorter than the vertex pitch 403 of the outer mesh layer 103. In some examples, this can be achieved by using different vertex shapes for the inner mesh layer 102 and the outer mesh layer 103. Alternatively, as previously mentioned and as shown in Figure 3, the holes 104 of each mesh layer 102, 103 may be arranged such that their elongated lengths 206 are orthogonal to each other. In this configuration, the ratio of the vertex pitch 403 of the outer mesh layer 103 to the vertex pitch 402 of the inner mesh layer 102 is the same as the ratio of the length 206 of the holes 104 to the width 207 in the mesh layers 102 and 103.

[0057] In examples where the inner mesh layer 102 and the outer mesh layer 103 are not nested to each other, they are not in contact in most places along their B-faces. In some examples, the inner mesh layer 102 and the outer mesh layer 103 may be configured such that their respective vertex pitches 402, 403 are not multiples of each other. In such examples, as shown in Figure 4, only a subset of the flat portions 205 of the B-faces of the inner mesh layers 102, 103 are in contact. These flat portions 205 function as point contact regions 401, where an interface is formed between the inner mesh layer 102 and the outer mesh layer 103.

[0058] In one embodiment, projection welding is used to join mesh layers 102 and 103. As current passes between the inner mesh layer 102 and the outer mesh layer 103, the current concentrates and flows through the point contact region 401. The high current causes resistance heating in the point contact region 401, resulting in the formation of a solid weld nugget that joins the mesh layers 102 and 103 together at their interface. In some examples, the weld nugget has an index size of 0.1 to 0.3 mm. In some examples, the contact regions on each mesh layer 102 and 103 are appropriately sized, and the forging pressure and heat input can be controlled to concentrate the current in the point contact region 401 to provide a weld without destroying the local structure of the mesh layers 102 and 103 or generating weld spatter (sudden ejection of molten metal away from the weld area). In one example, the contact area at each point contact region on their soft apex A side of the mesh layers 102 and 103 is 0.155 mm². 2 The length / width ratio is 11.5, and the contact area at each point contact region on the hard apex B side is 0.149 mm². 2 It can be molded such that the length / width ratio is 8.5.

[0059] In some examples, the formation of numerous weld nuggets increases the total interface area between mesh layers 102 and 103. This reduces the interfacial electronic contact resistance between parts, improving efficiency and lowering operating costs.

[0060] In some examples, the electrode assembly 100 may be assembled by first joining the inner surface of the inner mesh layer 102 to the surface of the porous sintered plate 101, and then joining the outer surface of the inner mesh layer 102 to the inner surface of the outer mesh layer 103.

[0061] In some examples, the efficiency of the electrolytic reaction can be increased when non-electrolyzed water is continuously supplied to all areas of the electrode assembly 100 to function as both reactant and coolant. The rhombic / diamond-shaped holes 104 in the mesh can facilitate biaxial flow of water pumped through the working electrolytic cell. The shorter dimension 207 of the rhombic shape may provide greater fluid resistance than the longer dimension, as measured by the permeability coefficient. This can alter the convection of water within the electrode assembly 100, preferentially overflowing the corners of the assembly 100 for efficient cooling and supply of reactant water to hard-to-reach areas, thereby maintaining a high stoichiometric ratio. A high stoichiometric ratio can be achieved in examples where the flow rate of water supplied to all corners of the electrode is greater than the rate at which water is consumed by the electrolytic reaction.

[0062] Figure 5 shows a layer 500 of the electrode assembly 100 containing multiple channels 501. In some examples, the channels 501 may be elongated channels formed on the surface of the mesh layer, providing conduits through which fluid can flow without obstruction. The channels 501 can further improve and direct fluid flow by directing the fluid across the surface of the assembly 100 and through the interior of the assembly 100, thereby directing a continuous supply of non-electrolyzed water to all areas of the assembly. In some examples, the channels can further control the removal of gases generated from the reaction.

[0063] In some examples, the channel 501 may extend across the entire surface of the mesh layer, delivering fluid in a controllable manner at discrete locations. Alternatively, the channel may extend only partway across the surface. In some examples, the channel may be located on the outermost layer of the assembly, i.e., the outer surface of the outer mesh layer 103. Alternatively, or additionally, other surfaces of the assembly may be provided with channel 501 to provide conduits for fluid flow through the interior of the assembly.

[0064] In some examples, the channel 501 can reduce the pumping loss of the electrode assembly 100 because the pressure required to continuously pump water into all areas of the assembly 100 may be lower. The channel 501 may extend from the edge of layer 500, as shown, to provide an access point and conduit for the fluid surrounding layer 500 to enter and flow through the electrode assembly 100. The channel 501 may also provide a path for gases generated by the electrolytic reaction to escape from the electrode assembly 100. In one example, the mesh layer may contain elongated holes, and the channel 501 may extend in a direction substantially perpendicular to the elongated direction of the holes. Flow parallel to the shorter dimension of the elongated holes is known to encounter greater fluid resistance than flow parallel to the elongated dimension, as measured by permeability coefficients and actual fluid flow experiments. Therefore, oriented the channel perpendicular to the elongated direction may help offset the increase in fluid resistance in this direction.

[0065] The channel 501 may be formed within the mesh layers 102, 103 during the manufacturing process of the mesh layers. Alternatively, the channel 501 may be added after manufacturing. In one example, the channel 501 is formed on the mesh layers 102, 103 using a low-tonnage press. Alternative methods for forming the channel 501 include pressing, embossing, rolling, or stamping the channel 501 onto the mesh layers 102, 103.

[0066] In one example, the channel 501 may be a microfluidic channel having a width and / or depth of less than 750 micrometers (μm). In some examples, microfluidic channels and meshes may exhibit hydrodynamic and mechanical advantages over macroscale fluid channels. In some examples, microfluidic channels may be manufactured without the use of large-tonnage presses. This may be beneficial because large-tonnage presses generally only move in one direction, and by using microfluidic channels, a larger and more flexible range of designs and patterns can be formed on the mesh layers 102, 103.

[0067] Figures 6a and 6b illustrate the configuration of an exemplary electrode assembly 100, in which the channels 501 are incorporated on the outer surface of the outer mesh layer 103. As with Figure 1, for clarity, the mesh layers 102 and 103 are shown in Figures 6a and 6b as flat sheets with small holes. Although the channels are shown only on a single surface of a single layer, in alternative embodiments, other surfaces of the electrode array may additionally or alternatively incorporate the channels 501. The channels 501 are shown as linear channels extending from one side to the other on the outer surface of the outer mesh layer 103. Alternatively, the channels 501 may have more complex paths and variable cross-sections. For example, the channels 501 may be curved or change direction, or one or more channels 501 may branch into separate channels and / or connect to other channels 501.

[0068] In one embodiment, the channel 501 has a variable cross-section, which is smaller at the inlet side of the electrode assembly and then larger as the channel 501 approaches the outlet side of the electrode assembly where the fluid-gas phase increases. This can enable a constant velocity of the fluid-gas phase and improved microfluidic control. Water electrolytic cells, in contrast to heat exchangers or fuel cells, generally operate with a mixed phase product. Thus, such a channel can help bring uniform coolant / gas distribution and supply to the porous sintered plate 101 in sufficient quantities across the entire cell plane by manipulating the ratio of the fluid velocity to its resistance. For example, the channel may have a convergence-divergence width and may form a Venturi tunnel that accelerates the flow through a particular region of the mesh layer. Furthermore, the variable cross-section channel 501 can work with the mesh layers 102, 103 to generate turbulence and vortices, which increase the film coefficient more than would occur in a straight channel 501. This can further improve the effectiveness in removing heat and promote a wider operating window with higher current densities.

[0069] Figure 6c shows a cross-sectional view of the assembly configuration in Figure 6b along plan AA. For clarity, in Figure 6c, the number of channels 501 is reduced and the scale of each channel 501 is increased compared to the channels 501 shown in Figure 6b. The channels 501 may have a rectangular cross-section as shown, but other cross-sections are also possible. The cross-section may also vary in shape and size along the channels 501 or between the channels 501.

[0070] Figure 7 shows an assembly 100 comprising a first inner mesh layer 102a and a second inner mesh layer 102b, a first outer mesh layer 103a bonded to the first inner mesh layer 102a, and a second outer mesh layer 103b bonded to the second inner mesh layer 102b. The first inner mesh layer 102a and the first outer mesh layer 103a are separated from the second inner mesh layer 102b and the second outer mesh layer 103b by a gap 701. The gap 701 may allow for the insertion of a structural member 702 to support the porous sintered plate 101 and the mesh layers 102, 103, thereby improving the rigidity and strength of the assembly 100. In some examples, the porous sintered plate 101 or one or more of the mesh layers 102, 103 may be bonded to a structural member. The gap 701 may also act as a large channel 501, providing a conduit for fluid to flow into and out of the assembly 100. The dimensions of the gap 701 may be larger than the dimensions of the inserted structural member to allow fluid to flow through the gap 701 around the structural member.

[0071] Similar to the assembly 100 comprising a single inner mesh layer 102 and an outer mesh layer 103, the assembly 100 shown in Figure 7 can be assembled by first bonding the first inner mesh layer 102a and the second inner mesh layer 102b to the porous sintered plate 101, and then subsequently bonding the first outer mesh layer 103a and the second outer mesh layer 103b to their respective inner mesh layers. The first inner mesh layer 102a and the second inner mesh layer 102b can be bonded to the porous sintered plate 101 sequentially in separate operations or simultaneously in a bonding operation. The first outer mesh layer 103a and the second outer mesh layer 103b can also be bonded to their respective inner mesh layers sequentially in separate operations or simultaneously in a bonding operation.

Claims

1. An electrode assembly for PEM electrolysis, Porous sintered plate and A first mesh layer comprising an expanded metal mesh, the first mesh layer having an inner surface bonded to the surface of the porous sintered plate, The assembly comprises a protective coating applied to the assembly, An electrode assembly in which the first mesh layer is bonded to the porous sintered plate at multiple point contact regions.

2. The assembly according to claim 1, further comprising a second mesh layer having an expanded metal mesh, wherein the second mesh layer has an inner surface joined to the outer surface of the first mesh layer in a plurality of point contact areas.

3. The first mesh layer and the second mesh layer are, One or more vertices, It comprises multiple point contact areas, The assembly according to claim 2, wherein each of the plurality of point contact regions is located at a vertex on the surface of each mesh layer.

4. The assembly according to claim 3, wherein each of the first mesh layer and the second mesh layer has a soft vertex face and a hard vertex face, the vertex of the soft vertex face is softer than the vertex of the hard vertex face, and the first mesh layer and the second mesh layer are joined together such that the soft vertex face of the second mesh layer faces outward.

5. At least one mesh layer, A mesh structure formed by multiple strands, The assembly according to any one of claims 1 to 4, comprising a plurality of diamond-shaped holes defined by the mesh structure, wherein the diamond-shaped holes have an acute angle of 53 to 58 degrees at the joint between strands.

6. The assembly according to any one of claims 3 to 5, wherein each of the point contact regions is located along the edge of a hole defined by the mesh structure of the first mesh layer.

7. The assembly according to any one of claims 1 to 6, wherein the first mesh layer comprises a mesh structure formed by a plurality of strands, and the strands of the first mesh layer have an average thickness of 0.3 to 0.6 mm.

8. The assembly according to any one of claims 1 to 7, wherein the first mesh layer has an open volume of 60% to 80% and a front opening area of ​​at least 35%.

9. If dependent on claim 2, Each of the first mesh layer and the second mesh layer has a mesh structure, and the mesh structure includes a plurality of holes, when assembled, The plurality of holes in the mesh structure of the first mesh layer are extended in the first direction, The plurality of holes in the mesh structure of the second mesh layer extend in the second direction, and The assembly according to any one of claims 1 to 8, wherein the first direction and the second direction are orthogonal to each other.

10. The assembly according to any one of claims 1 to 9, wherein the flatness of the outermost surface of the electrode assembly is 0.01 to 0.03 mm per meter.

11. The assembly according to any one of claims 1 to 10, wherein, in the case of claim 2, the first mesh layer is joined to the second mesh layer and one of the porous sintered plates with a joint coverage of 15% or more of the area of ​​the electrode assembly.

12. If dependent on claim 2, A third metal mesh layer comprising an expanded metal mesh, the third metal mesh layer having an inner surface bonded to the surface of the porous sintered plate, A fourth mesh layer comprising an expanded metal mesh, the fourth mesh layer having an inner surface joined to the outer surface of the third mesh layer, further comprising: The assembly according to any one of claims 1 to 11, wherein the third and fourth mesh layers are separated from the first and second mesh layers.

13. The assembly according to any one of claims 1 to 12, wherein the porous sintered plate contains titanium, and at least one of the one or more mesh layers contains titanium.

14. The assembly according to any one of claims 1 to 13, wherein the protective coating comprises platinum or a mixed precious metal oxide.

15. The assembly according to any one of claims 1 to 14, wherein the porous sintered plate comprises a plurality of porous networks.

16. Preferably, a porous sintered plate comprising a microporous coating formed from at least two different grades of sintered powder.

17. The assembly according to any one of claims 1 to 16, wherein at least one of the one or more mesh layers has at least one flow path on the surface of the mesh layer.

18. The assembly according to claim 17, wherein one of the at least one flow channels has a nonlinear shape.

19. The assembly according to claim 17 or 18, wherein each of the at least one flow channels is a microfluidic flow channel having a diameter of less than 750 μm perpendicular to the flow direction.

20. The assembly according to any one of claims 1 to 19, wherein the electrode assembly has an active region of 1,000 to 2,100 square centimeters.

21. The assembly according to any one of claims 1 to 20, wherein the electrode assembly has a thickness of 1.1 to 2.8 mm.

22. A method for manufacturing an electrode assembly for PEM electrolysis, The steps include forming an electrode assembly by joining the inner surface of a first mesh layer, which comprises an expanded metal mesh, to the surface of a porous sintered plate, The step of applying a protective coating to the electrode assembly is included. A method in which the first mesh layer is joined to the sintered plate at a plurality of point contact regions.

23. The method according to claim 22, further comprising joining a second mesh layer comprising an expanded metal mesh to the outer surface of the first mesh layer, wherein the first mesh layer is joined to the second mesh layer at a plurality of point contact areas.

24. The method according to claim 23 or 24, wherein the step of bonding the first mesh layer to the surface of the porous sintered plate is followed by the step of bonding the second mesh layer to the outer surface of the first mesh layer.

25. The method according to any one of claims 23 to 25, wherein projection welding is used to join the first mesh layer to the porous sintered plate and to join the first mesh layer to the second mesh layer.

Images