Gas-permeable and electronically conductive plate for use as a porous transport layer of an electrolytic cell

Abstract

A gas-permeable electronically conductive plate for use as a porous transport layer of an electrolytic cell, a method for manufacturing the gas-permeable electronically conductive plate, a building unit for an electrolytic cell, and an electrolytic cell are described.

Description

Technical Field

[0001] A gas-permeable electronically conductive plate for use as a porous transport layer of an electrolytic cell, and a method for manufacturing the gas-permeable electronically conductive plate are described. Also described are a building unit for an electrolytic cell and an electrolytic cell.

Background Art

[0002] In an electrolytic cell that generates gaseous products such as hydrogen and oxygen, transport passages for liquid products such as water and gaseous products such as oxygen and hydrogen are provided by a porous transport layer. The porous transport layer must simultaneously provide electrical contact between a bipolar plate adjacent to a first surface of the porous transport layer and a catalyst layer adjacent to a second surface of the porous transport layer. Thus, such a porous transport layer is required to have a low pressure loss for promoting fluid transport and a large contact area with the catalyst layer for ensuring maximum utilization of the catalyst. The two requirements are contradictory. This is because in order to maximize the catalyst interface, it is necessary to reduce the pore size to reduce mass transfer, while in order to maximize mass transfer, it is necessary to increase the pore size to minimize the interface with the catalyst interface.

[0003] The related prior art is as follows: CN111621806A EP3686318A1 JP2009181918A EP3939722A1 US2015 / 376800A1 It is.

[0004] US2005 / 181264A1. The unpublished PCT application WO2023 / 061869 by the same applicant discloses a porous transport layer of a proton exchange membrane (PEM)-structured electrolytic cell. The porous transport layer has a two-layer structure or a multi-layer structure. Each of the layers of the two-layer structure or the multi-layer structure has different average pore diameters and / or different porosities, and the layer having the highest porosity and / or the highest average pore diameter is in contact with the bipolar plate, and the layer having the lowest porosity and / or the lowest average pore diameter is arranged to be in contact with the catalyst layer. The multi-layer structure can be obtained by co-extruding different mixtures each containing metal particles and a polymer binder. The porosity and / or pore diameter of the co-extruded layer are controlled by appropriately adjusting one or both of the average particle size of the metal particles and the content of the metal particles in the co-extruded mixture. The higher the average particle size of the metal particles in the mixture, the higher the pore diameter and porosity of the resulting layer. The higher the content of the metal particles in the mixture, the lower the pore diameter and porosity of the resulting layer. Such adjustment of the average pore diameter and porosity is advantageous. Nevertheless, in such a porous transport layer, fluid transport is only possible through the pores, and there are certain limits for reasons of stability in increasing the average pore diameter and porosity. Furthermore, the pores are necessarily tortuous, which imposes further limitations on fluid transport.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

[0006] Therefore, there is a need for a porous transport layer that increases fluid transport without compromising electronic contact and mechanical stability with the catalyst layer. The present invention relates to solving the contradictory relationship between the requirement of maximizing the catalyst interface of the porous transport layer and the requirement of maximizing fluid transport through the porous transport layer. MEANS FOR SOLVING THE PROBLEM

[0007] To solve this problem, according to a first aspect, there is provided a gas-permeable electronically conductive plate for use as a porous transport layer of an electrolytic cell. The gas-permeable plate - contains one or more metal particles selected from the group consisting of titanium, titanium alloys, and stainless steel, - has a plurality of pores having an average pore diameter, - has a first surface and a second surface facing each other, and a thickness dimension extending perpendicular to the first surface and the second surface, The first surface of the gas-permeable electronically conductive plate has one or more recesses extending in the thickness direction of the gas-permeable electronically conductive plate from the first surface, The recess has a lateral dimension on the first surface of the gas-permeable electronically conductive plate that is larger than the average pore diameter of the pores. BRIEF DESCRIPTION OF THE DRAWINGS

[0008]

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DETAILED DESCRIPTION OF THE INVENTION

[0009] The gas permeable electronically conductive plate according to the first aspect comprises or consists of one or more metal particles selected from titanium, titanium alloys and stainless steel. A mixture of metal particles selected from titanium, titanium alloys and stainless steel is also possible. The metal particles consist essentially of one or more selected from the group consisting of titanium, titanium alloys and stainless steel. The presence of trace amounts of other components, in particular inevitable impurities that do not have an adverse effect on the chemical and mechanical properties of the metal particles, is not excluded.

[0010] Preferably, the metal particles forming the gas permeable electronically conductive plate are sintered together. The composition of the metal particles may be varied along the thickness dimension of the gas permeable electronically conductive plate.

[0011] The gas-permeable and electronically conductive plate has a first surface configured to contact the bipolar plate of the electrolytic cell and a second surface configured to contact the catalyst layer of the electrolytic cell. The first surface and the second surface of the gas-permeable and electronically conductive plate face each other. The first surface and the second surface are the largest surfaces of the gas-permeable and electronically conductive plate. The dimension of the gas-permeable and electronically conductive plate extending perpendicular to the first surface and the second surface is referred to as the thickness dimension of the gas-permeable and electronically conductive plate.

[0012] The gas-permeable and electronically conductive plate is porous. The pores extend between the metal particles. Preferably, the gas-permeable and electronically conductive plate according to the present invention has a porosity in the range of 10% to 80% by volume, preferably 30% to 60% by volume, as measured by volume intrusion mercury porosimetry in accordance with DIN66133. The pores have a dimension referred to as the average pore diameter. Preferably, the average pore diameter is in the range of 5 μm to 40 μm as measured by volume intrusion mercury porosimetry in accordance with DIN66133. More preferably, the porosity is in the range of 10% to 80% by volume, preferably 30% to 60% by volume, as measured by volume intrusion mercury porosimetry in accordance with DIN66133, and the average pore diameter is in the range of 5 μm to 40 μm as measured by volume intrusion mercury porosimetry in accordance with DIN66133.

[0013] Both the porosity and the pore diameter can vary along the thickness dimension of the gas-permeable and electronically conductive plate. Preferably, the porosity and / or the average pore diameter decrease in the direction from the first surface to the second surface of the gas-permeable and electronically conductive plate, the porosity and / or the average pore diameter reach a maximum at the first surface of the gas-permeable and electronically conductive plate configured to contact the bipolar plate, and the porosity and / or the average pore diameter reach a minimum at the second surface of the gas-permeable and electronically conductive plate configured to contact the catalyst layer.

[0014] The change in porosity and / or average pore diameter along the thickness dimension may be stepwise (resulting in a two-layer or multi-layer structure of the gas-permeable electronically conductive plate) or substantially continuous. A method for preparing a gas-permeable electronically conductive plate having a multi-layer structure is described in the unpublished PCT application WO2023 / 061869 of the same applicant.

[0015] The first surface of the gas-permeable electronically conductive plate has one or more recesses extending in the thickness direction of the gas-permeable electronically conductive plate from the first surface. Each of the recesses has a lateral dimension at the first surface of the gas-permeable electronically conductive plate, i.e., a lateral dimension measured at the level of the first surface of the gas-permeable electronically conductive plate. Each of the recesses has a dimension extending in the thickness direction of the gas-permeable electronically conductive plate. The dimension extending in the thickness direction of the gas-permeable electronically conductive plate is referred to as the depth of the recess.

[0016] The one or more recesses function as passages for fluid flow.

[0017] For example, such a recess extends from the first surface through the entire thickness of the gas-permeable electronically conductive plate and thus reaches the second surface of the gas-permeable electronically conductive plate. This type of recess has a depth equal to the thickness of the gas-permeable electronically conductive plate and is referred to as a through-hole. This type of recess promotes the transport of each fluid from and towards the catalyst layer across the gas-permeable electronically conductive plate.

[0018] Alternatively, such a recess extends from the first surface of the gas-permeable electronically conductive plate to a depth less than the total thickness of the gas-permeable electronically conductive plate and does not reach the second surface of the gas-permeable electronically conductive plate. Such a recess having a depth less than the thickness of the gas-permeable electronically conductive plate may be in the form of a groove or a dimple, or may be in the form of a recessed region extending around one or more island-like (i.e., island-shaped) non-recessed portions. Combinations of different types of recesses are also possible. This type of recess facilitates lateral fluid transport in the gas-permeable electronically conductive plate and shortens each of the travel distances for the reactants to reach the catalyst layer via the pores and to be removed from the catalyst layer.

[0019] Details of different types of recesses will be described later.

[0020] Each of the recesses has a lateral dimension at the first surface of the gas-permeable electronically conductive plate, i.e., the lateral dimension measured at the level of the first surface of the gas-permeable electronically conductive plate. In the case of a recess in the form of a through-hole, the lateral dimension corresponds to the width of the through-hole measured at the level of the first surface of the gas-permeable electronically conductive plate. In the case of a recess in the form of a dimple or a groove, the lateral dimension corresponds to the width of the dimple or the groove measured at the level of the first surface of the gas-permeable electronically conductive plate. In the case of a recessed region extending around one or more island-like (island-shaped) non-recessed portions, the dimension is the distance between the edges of adjacent non-recessed portions measured at the level of the first surface of the gas-permeable electronically conductive plate.

[0021] The lateral dimension of the recesses at the first surface of the gas-permeable electronically conductive plate is larger than the average pore diameter. Thus, the recesses can significantly reduce the pressure loss in the porous transport layer compared to a porous transport layer having the same design except for the absence of the recesses, such that mass transfer is achieved only through the pores. Further, the contact area between the porous transport layer and the catalyst is maintained or does not substantially decrease compared to a porous transport layer having the same design except for the absence of the recesses.

[0022] The thickness of the gas-permeable and electronically conductive plate refers to a position without a recess and is understood to be determined at a position without a recess. Preferably, the gas-permeable and electronically conductive plate according to the present invention has a thickness in the range of 20 μm to 2000 μm when measured at a position without a recess.

[0023] In a first preferred embodiment, the gas-permeable and electronically conductive plate has one or more recesses in the form of through-holes extending from the first surface to the second surface of the gas-permeable and electronically conductive plate, and the through-holes are hereinafter - a central axis extending perpendicularly from the first surface to the second surface of the gas-permeable and electronically conductive plate, and - a width at the level of the first surface of the gas-permeable and electronically conductive plate and has.

[0024] Such through-holes may have a circular, elliptical, square, polygonal, or any other suitable contour. The width of the through-hole at the level of the first surface of the gas-permeable and electronically conductive plate is larger than the average pore diameter of the pores of the gas-permeable and electronically conductive plate. Preferably, the width of the through-hole at the level of the first surface of the gas-permeable and electronically conductive plate is in the range of 20 μm to 1000 μm, preferably 40 μm to 800 μm, more preferably 50 μm to 600 μm. In the case of a through-hole having a circular contour, the width corresponds to the diameter of the through-hole. A through-hole having a diameter or width that tapers in the direction from the first surface to the second surface of the gas-permeable and electronically conductive plate and that reduces the loss at the contact interface with the catalyst layer at the second surface of the gas-permeable and electronically conductive plate is preferred. Compared with pores, such through-holes show substantially no flexibility, so that mass transfer is promoted and pressure loss is reduced.

[0025] In addition to the through-holes, the gas-permeable electronic conductive plate according to the first embodiment may have one or more recesses on the first surface, and the recesses have a depth less than the thickness of the gas-permeable electronic conductive plate at the non-recessed position. Such recesses may be in the form of depressions or grooves, or may be in the form of a recessed area extending around one or more island-like (island-shaped) non-recessed portions (see below for details). Combinations of different types of such recesses are also possible.

[0026] In a second preferred embodiment, the gas-permeable electronic conductive plate has one or more recesses on the first surface having a depth less than the thickness of the gas-permeable electronic conductive plate at the non-recessed position, and there are no recesses having a depth equal to the thickness of the gas-permeable electronic conductive plate. Thus, in the second embodiment, the gas-permeable electronic conductive plate does not have through-holes as defined above in the context of the first embodiment.

[0027] In the gas-permeable electronic conductive plate according to the first embodiment or the second embodiment, one or more of the recesses on the first surface having a depth less than the thickness of the gas-permeable electronic conductive plate may be in the form of depressions. The width of the depression at the level of the first surface of the gas-permeable electronic conductive plate is larger than the average pore diameter of the pores of the gas-permeable electronic conductive plate. Preferably, the depression has a width of 10 μm to 5000 μm at the level of the first surface of the gas-permeable electronic conductive plate. Such depressions may have a circular, elliptical, square, polygonal, or any other suitable contour. In the case of a circular depression, the width corresponds to the diameter of the depression. Such depressions may have a U-shaped, V-shaped (triangular), square, semi-circular, or any other suitable cross-section.

[0028] The recesses in the form of depressions are more advantageous than the recesses in the form of through-holes. This is because the contact loss with the catalyst layer is avoided on the second surface of the gas-permeable electronic conductive plate, and the loss of the electronically conductive material within the gas-permeable electronic conductive plate is reduced.

[0029] The recesses in the form of dimples are more advantageous than the recesses in the form of grooves (channels). This is because the dimples enable one-dimensional mass transport of oxygen along the thickness direction of the gas-permeable and electronically conductive plate perpendicular to the flow-field of the adjacent bipolar plates. In contrast, in the case of grooves, the mass transport of oxygen first enters in the direction of the grooves through the thickness of the gas-permeable and electronically conductive plate, and then becomes two-dimensional in the lateral direction along the grooves. Therefore, in order to optimize the mass transport of oxygen through the recesses in the form of grooves, the pattern of the grooves on the gas-permeable and electronically conductive plate must be designed to cooperate with the structure of the flow-field on the adjacent surfaces of the bipolar plates (see below). In contrast, dimples easily cooperate with a variety of flow-field structures.

[0030] In the gas-permeable and electronically conductive plate having recesses in the form of dimples, the dimples provide a mass transport path with reduced flow resistance for transporting the oxygen generated in the catalyst layer toward the bipolar plate. On the other hand, the adjacent non-recessed porous portions of the gas-permeable and electronically conductive plate provide a mass transport path for transporting water toward the catalyst layer by capillary force. In this way, a plurality of separated transport paths for oxygen and a plurality of separated transport paths for water are formed extremely close to each other.

[0031] Furthermore, the recesses in the form of dimples are preferable with respect to the mechanical stability of the gas-permeable and electronically conductive plate. In contrast, the recesses in the form of grooves may become a seeding point for fracture when the gas-permeable and electronically conductive plate is subjected to bending stress.

[0032] In the preferred gas-permeable and electronically conductive plate according to the present invention, all the recesses are in the form of dimples, and the dimples are uniformly distributed on the first surface of the gas-permeable and electronically conductive plate.

[0033] The gas-permeable and electronically conductive plate may have a two-layer structure (as described above) composed of a first layer and a second layer. The first layer configured to contact the bipolar plate has a higher porosity and / or a larger average pore diameter than the second layer configured to contact the catalyst layer. When the gas-permeable and electronically conductive plate has such a two-layer structure, it is preferable that the depth of the recess extends over 80% to 100%, preferably 90% to 100% of the thickness of the first layer having a higher porosity and / or a larger average pore diameter. When the depth of the recess extends over 100% of the thickness of the first layer having a higher porosity and / or a larger average pore diameter, the depth of the recess may further extend over at most 50%, preferably at most 10% of the thickness of the second layer having a lower porosity and / or a smaller average pore diameter. Therefore, when the depth of the recess extends over 100% of the thickness of the first layer, the depth of the recess may further extend over 0% to 50%, preferably 0% to 10% of the thickness of the second layer.

[0034] Restricting the depth of the recess in this way has the advantage of avoiding excessive densification of the porous structure near the second surface of the gas-permeable and electronically conductive plate configured to contact the catalyst layer, or even avoiding deformation of the second surface of the gas-permeable and electronically conductive plate.

[0035] In the gas-permeable and electronically conductive plate according to the first or second embodiment, one or more of the recesses on the first surface having a depth less than the thickness of the gas-permeable and electronically conductive plate may be in the form of grooves. The width of the groove at the level of the first surface of the gas-permeable and electronically conductive plate is larger than the average pore diameter of the pores of the gas-permeable and electronically conductive plate. Preferably, the groove has a width of 10 μm to 5000 μm measured at the level of the first surface of the gas-permeable and electronically conductive plate. The groove may have a straight, zigzag, zigzag, meandering, honeycomb, or any other suitable path. Such a groove may have a U-shaped, V-shaped (triangular), angular, square, semicircular, or any other suitable cross-section. The groove may form a continuous channel extending from the fluid inlet to the fluid outlet.

[0036] In the gas-permeable electronically conductive plate according to the first or second embodiment, a recess on the first surface having a depth less than the thickness of the gas-permeable electronically conductive plate extends around one or more island-like (island-shaped) non-recessed portions. Each non-recessed portion has a top surface at the level of the first surface of the gas-permeable electronically conductive plate. The recessed region surrounding the non-recessed portion provides a passage for fluid flow around the non-recessed portion that provides electrical contact with the bipolar plate. The lateral distance between the edges of adjacent non-recessed portions at the level of the first surface of the gas-permeable electronically conductive plate is greater than the average pore diameter of the pores of the gas-permeable electronically conductive plate. Preferably, the lateral distance between the edges of adjacent non-recessed portions of the first surface is in the range of 20 μm to 5000 μm as measured at the level of the first surface. The island-like (island-shaped) non-recessed portions may have the shape of ridges, dams, columns, pillars, honeycombs, truncated pyramids, truncated cones, stepped or staircase-like structures (i.e., structures that taper towards the first surface of the gas-permeable electronically conductive plate), or any other suitable structure. Combinations of non-recessed portions having different structures are also possible.

[0037] Most preferably, the gas-permeable electronically conductive plate according to the first aspect defined above is applied as a porous transport layer on the anode side of the electrolytic cell of an electrolyzer for the electrolysis of water in which oxygen is formed. Here, since the pressure loss is advantageously low, the gas-permeable electronically conductive plate according to the first aspect defined above promotes the transport of water to the porous transport layer and the outflow of generated oxygen from the porous transport layer.

[0038] According to a second aspect, a building unit for an electrolyzer is provided. The building unit comprises, hereinafter, - a gas-permeable electronically conductive plate according to the first aspect defined above and - hereinafter, - a gas-impermeable electronically conductive bipolar plate in contact with the first surface of the gas-permeable electronically conductive plate, and - A catalyst layer in contact with the second surface of the gas-permeable electronically conductive plate and at least one of comprises or consists of them.

[0039] Electrolytic cells are known in the art. Basically, an electrolytic cell includes a plurality of identical adjacent electrochemical cells electrically connected in series via gas-impermeable electronically conductive bipolar plates.

[0040] In a building unit according to a second aspect, the gas-permeable electronically conductive plate according to the first aspect defined above functions as a porous transport layer. It preferably has one or more of the preferred features defined above and / or is selected from the preferred embodiments defined above.

[0041] In a building unit according to a second aspect, the catalyst layer preferably comprises a catalyst capable of catalyzing an electrochemical oxygen generation reaction or a hydrogen generation reaction. The catalyst is preferably selected from the group consisting of iridium, iridium oxide, platinum, platinum oxide, palladium, palladium oxide, ruthenium, ruthenium oxide, and mixtures of the oxides listed herein. The catalyst is either non-supported or supported on a suitable catalyst support, for example, a catalyst support selected from the group consisting of SnO2, TiO2, and carbon black.

[0042] In a building unit according to a second aspect, the catalyst layer is preferably an anode catalyst layer and comprises a catalyst capable of catalyzing electrochemical oxygen generation.

[0043] In a first preferred embodiment, a building unit according to the second aspect defined above is hereinafter - A gas-permeable electronically conductive plate according to the first aspect defined above, wherein the recess on the first surface of the gas-permeable electronically conductive plate preferably has a lateral dimension in the range of 100 μm to 5000 μm, a gas-permeable electronically conductive plate, and - A gas-impermeable electronically conductive bipolar plate having a surface in contact with the first surface of the gas-permeable electronically conductive plate, wherein the surface of the bipolar plate in contact with the first surface of the gas-permeable electronically conductive plate has no recesses, and the gas-impermeable electronically conductive bipolar plate comprises or consists of them.

[0044] In such an embodiment, the bipolar plate only provides electrical contact between adjacent cells of the electrolytic cell and does not provide any fluid flow structure. Any reactant transport is carried out within the gas-permeable electronically conductive plate. In order to facilitate lateral reactant transport, it is preferred that the gas-permeable electronically conductive plate has at least one recess in the form of a continuous channel extending around non-recessed portions such as a plurality of islands (island-shaped) or in the form of a continuous concave region. Continuous means that the recess extends from a fluid inlet connected to the fluid supply manifold of the electrolytic cell to a fluid outlet connected to the fluid removal manifold of the electrolytic cell. The recesses on the first surface of the gas-permeable electronically conductive plate preferably have a lateral dimension (e.g., channel width) in the range of 100 μm to 5000 μm. This dimension is in the same range as the lateral dimension (e.g., channel width) of the flow field structure of a bipolar plate of the state-of-the-art commonly used.

[0045] This embodiment has the advantages that the design of the building unit and the corresponding electrolytic cell is rationalized, and the manufacture of the bipolar plate is simplified. This is because the provision of the flow field to the bipolar plate is omitted. Furthermore, since the thickness of the bipolar plate is reduced, the space requirement is reduced, and the volumetric specific output of the electrolytic cell is improved.

[0046] Furthermore, since the fluid flow completely transfers to the porous transport layer, the reactants move through the entire thickness of the porous transport layer and do not need to reach the catalyst layer. By reducing the distance that the reactants have to move to reach the catalyst layer, the access of the reactants to the catalyst layer is improved, and the performance and yield of the electrolytic cell are improved.

[0047] In a second preferred embodiment, the building unit according to the second aspect is hereinafter - a gas-permeable electronically conductive plate according to the first aspect defined above, and - a gas-impermeable electronically conductive bipolar plate having a flow field surface in contact with the first surface of the gas-permeable electronically conductive plate, and includes or consists of these, the flow field surface of the bipolar plate has a fluid flow structure including recesses extending between protruding (i.e., non-recessed) regions, and one or more of the protruding (non-recessed) regions extend across one or more of the recesses on the first surface of the gas-permeable electronically conductive plate. Preferably, the protruding regions on the flow field surface of the bipolar plate have a lateral dimension that is greater than the lateral dimension of the recesses on the first surface of the gas-permeable electronically conductive plate.

[0048] In such an embodiment, the bipolar plate and the adjacent first surface of the gas-permeable electronically conductive plate according to the first aspect defined above cooperate in providing a fluid flow structure for reactant transport.

[0049] The bipolar plate has a flow field surface in contact with the first surface of the gas-permeable electronically conductive plate defined above. As described above, the first surface of the gas-permeable electronically conductive plate has one or more recesses extending in the thickness direction of the gas-permeable electronically conductive plate from the first surface. The flow field surface of the bipolar plate has a fluid flow structure including recesses extending between protruding (i.e., non-recessed) regions. Such a fluid flow structure is also referred to as a flow field. Suitable flow field designs are known in the art. Typically, the flow field includes at least one recess forming a continuous channel extending between two protruding regions providing the walls of the channel. Continuous means that the recess extends from a fluid inlet connected to the fluid supply manifold of the electrolytic cell to a fluid outlet connected to the fluid removal manifold of the electrolytic cell.

[0050] In the building unit according to the second embodiment defined above, one or more of the protruding (non-recessed) regions of the flow field surface of the bipolar plate extend, in each case, across one or more of the recesses of the first surface of the gas-permeable electronically conductive plate adjacent to the flow field surface of the bipolar plate.

[0051] Preferably, the protruding (non-recessed) region on the flow field surface of the bipolar plate has a transverse dimension that is larger than the transverse dimension of the recess on the first surface of the gas-permeable electronically conductive plate adjacent to the flow field surface of the bipolar plate. Here, the transverse dimension of the protruding (non-recessed) region on the flow field surface of the bipolar plate is preferably in the range of 100 μm to 5000 μm, and the transverse dimension of the recess on the first surface of the gas-permeable electronically conductive plate is preferably in the range of 10 μm to 1000 μm.

[0052] This embodiment has the advantage that mass transfer to and from the region of the gas-permeable electronically conductive plate covered by the protruding (non-recessed) regions of the flow field surfaces of adjacent bipolar plates is improved. More specifically, the presence of the lateral outflow passages provided by one or more recesses on the first surface of the gas-permeable electronically conductive plate that cooperate with the pores of the gas-permeable electronically conductive plate promotes the outflow of gaseous electrolysis products such as hydrogen and oxygen into the flow field channels. Thus, the homogeneity of mass transfer and the current distribution across the region of the porous transport layer are also improved, which enables a higher current density and prevents the formation of "hot spots". Therefore, the operating safety, performance, and yield of the electrolytic cell are improved.

[0053] According to a third aspect, hereinafter, - a gas-permeable electronically conductive plate according to the first aspect defined above or - a building unit according to the second aspect defined above An electrolytic cell is provided that includes.

[0054] In the electrolytic cell according to the third aspect, each of the gas-permeable electron-conductive plate according to the first aspect defined above and the building unit according to the second aspect defined above preferably has one or more of the preferred features defined above and / or is selected from the preferred embodiments defined above.

[0055] Preferably, the electrolytic cell is an electrolytic cell for electrolysis of water containing an electrolyte in the form of a proton exchange membrane.

[0056] According to a fourth aspect, a method for preparing a gas-permeable electron-conductive plate according to the first aspect is provided. The method includes the following steps: (i) forming a mixture containing one or more metal particles selected from the group consisting of titanium, titanium alloys, and stainless steel and a polymer binder to obtain a green body plate, wherein the green body plate has a first surface and a second surface facing each other, and a thickness dimension extending perpendicular to the first surface and the second surface, wherein the first surface of the green body plate has one or more recesses extending in the thickness direction of the green body plate from the first surface, wherein the recess has a lateral dimension in the range of 11 μm to 5500 μm on the first surface, step; (ii) debinding the green body plate prepared in step (i) to obtain a brown body plate, (iii) sintering the brown body plate obtained in step (ii) in a non-oxidizing atmosphere or under vacuum to form a gas-permeable electron-conductive plate is included.

[0057] The green body plate obtained in step (i) has a first surface and a second surface facing each other. The first surface and the second surface are the largest surfaces of the green body plate. The dimension of the green body plate extending perpendicular to the first surface and the second surface is referred to as the thickness of the green body plate.

[0058] In step (i) of the method according to the fourth aspect, hereinafter, - one or more metal particles selected from the group consisting of titanium, titanium alloys, and stainless steel, - a polymer binder A mixture containing or consisting of these is formed into a green body plate. In the mixture, preferably, the volume fraction of the metal particles is in the range of 40% to 70% by volume, more preferably 45% to 65% by volume, and the volume fraction of the polymer binder is in the range of 30% to 60% by volume, preferably 35% to 55% by volume, all of which are values relative to the total volume of the mixture. Techniques for preparing such mixtures are known in the art.

[0059] The mixture may be in the form of a powder mixture or a slurry containing metal particles and a binder. Alternatively, the mixture may be in the form of granules obtained by compounding metal particles with a liquid binder, a liquefied binder, or a solid binder. Compounding techniques are known in the art. Typically, compounding is carried out by a compounder (e.g., a twin-screw extruder, a kneader, a planetary extruder) or an extruder.

[0060] The metal particles are selected from one or more of titanium, titanium alloys, and stainless steel. A mixture of metal particles selected from titanium, titanium alloys, and stainless steel is also possible. The metal particles consist essentially of one or more selected from the group consisting of titanium, titanium alloys, and stainless steel. The presence of trace amounts of other components, especially inevitable impurities that do not have an adverse effect on the chemical and mechanical properties of the metal particles, is not excluded.

[0061] Preferably, the metal particles have an average particle size of 15 μm to 106 μm as measured by the laser diffraction method. The average particle size of the metal particles may vary along the thickness direction of the green body plate. The change in the average particle size of the metal particles along the thickness dimension may be stepwise (resulting in a two-layer or multi-layer structure of the gas-permeable electron-conductive plate) or substantially continuous. By adjusting the particle size of the metal particles in the mixture, the average pore diameter of the resulting gas-permeable electron-conductive plate can be controlled. The average pore diameter increases as the average particle size of the metal particles increases. Preferably, the average particle size of the metal particles decreases along the thickness in the direction from the first surface to the second surface of the green body plate formed in step (i). As a result, in the resulting gas-permeable electron-conductive plate, the average pore diameter reaches its maximum at the first surface of the gas-permeable electron-conductive plate configured to contact the bipolar plate, and the average pore diameter reaches its minimum at the second surface of the gas-permeable electron-conductive plate configured to contact the catalyst layer.

[0062] A method for obtaining such a multi-layer structure is described in the unpublished PCT application WO2023 / 061869 of the same applicant.

[0063] The desired particle size distribution of the metal particles is obtained by sieving or classification.

[0064] Techniques for obtaining the metal particles used in the method defined above are known in the art. For example, a metal material selected from titanium, titanium alloys, and stainless steel is pulverized into particles. The pulverization is performed using a classifier mill, a hammer mill, or a ball mill. Alternatively, the metal particles used in the method defined above may be obtained by atomization. Any suitable technique may be used for the atomization of a material selected from titanium, titanium alloys, and stainless steel. Such techniques are known in the art. Suitable atomization techniques for titanium are, for example, plasma atomization (PA), electrode inert gas atomization (EIGA), and hydrogenation dehydrogenation (HDH).

[0065] Plasma treatment of metal particles may be performed to improve the sphericity of the metal particles and remove contaminants.

[0066] Suitable binders are known in the art. Typically, the binder is an organic polymer.

[0067] Preferred binders are as follows, (b1) 40 to 97.5% by mass of one or more polyoxymethylenes (POM), (b2) 1 to 35% by mass of one or more polyolefins (PO), (b3) without further polymer (FP), or 0.5 to 20% by mass of one or more further polymers (FP), and (b4) without dispersant, or 0 to 5% by mass of at least one dispersant comprising or consisting essentially of these, where these are in each case relative to the total mass of the binder, and the mass percentages of (b1), (b2), (b3) and (b4) total 100%. In the said binder, POM is different from PO, PO is different from FP, FP is different from the dispersant, and the dispersant is different from POM.

[0068] The term "polyoxymethylene" or "POM" encompasses POM itself, namely polyoxymethylene homopolymers, polyoxymethylene copolymers, and polyoxymethylene terpolymers. One or more polyolefins are preferably selected from the group consisting of polymethylpentene, poly-1-butene, polyisobutylene, polyethylene, and polypropylene. One or more additional polymers are preferably selected from the group consisting of polyethers, polyurethanes, polyepoxides, polyamides, vinyl aromatic polymers, poly(vinyl esters), poly(vinyl ethers), poly(alkyl (meth)acrylates), and their copolymers. One or more dispersants are preferably selected from the group consisting of oligomeric polyethylene oxides having a low molecular weight of 200 to 600 g / mol, stearic acid, stearamide, hydroxystearic acid, fatty alcohols, fatty alcohol sulfonates, and block copolymers of ethylene oxide and propylene oxide, and particularly preferably fatty acid esters.

[0069] The preparation of the binder and its components (b1) to (b4) defined above is known in the art. For details, refer to the unpublished PCT application WO2023 / 061869 by the same applicant.

[0070] The green body plate formed in step (i) contains, or consists of a mixture containing, or consists of one or more metal particles selected from the group consisting of titanium, titanium alloys, and stainless steel, and a polymer binder. In the green body plate, the metal particles are held together by the binder.

[0071] The volume ratio between the metal particles and the binder may vary along the thickness direction of the gas-permeable and electronically conductive plate. The change in the volume ratio between the metal particles and the binder along the thickness dimension may be stepwise (resulting in a two-layer or multi-layer structure of the gas-permeable and electronically conductive plate) or substantially continuous. Preferably, the volume ratio between the metal particles and the binder increases along the thickness in the direction from the first surface to the second surface of the green body plate formed in step (i), and / or the average particle size of the metal particles decreases along the thickness in the direction from the first surface to the second surface of the green body plate formed in step (i), such that in the resulting gas-permeable and electronically conductive plate, the average pore diameter reaches a maximum at the first surface of the gas-permeable and electronically conductive plate configured to contact the bipolar plate, and the average pore diameter reaches a minimum at the second surface of the gas-permeable and electronically conductive plate configured to contact the catalyst layer.

[0072] A method for obtaining such a multi-layer structure is described in the unpublished PCT application WO2023 / 061869 of the same applicant.

[0073] The first surface of the green body plate has one or more recesses extending in the thickness direction of the green body plate from the first surface. Each of the recesses has a lateral dimension at the first surface of the green body plate, i.e., a lateral dimension measured at the level of the first surface of the green body plate. Each of the recesses has a dimension extending in the thickness direction of the green body plate. The dimension extending in the thickness direction of the green body plate is referred to as the depth of the recess.

[0074] For example, such a recess extends from the first surface through the entire thickness of the green body plate and thus reaches the second surface of the green body plate in this way. This type of recess has a depth equal to the thickness of the green body plate and is referred to as a through-hole. Alternatively, such a recess extends from the first surface to a depth less than the entire thickness of the green body plate and does not reach the second surface of the green body plate. Such a recess having a depth less than the thickness of the green body plate may be in the form of a groove or a depression, or may be in the form of a recessed area extending around one or more island-like (island-shaped) non-recessed portions. Combinations of different types of recesses are also possible. Details of different types of recesses were described above in the context of the first aspect.

[0075] Each of the recesses has a lateral dimension on the first surface of the green body plate, i.e., a lateral dimension measured at the level of the first surface of the green body plate. In the case of a recess in the form of a through-hole (for example, having a circular contour), the lateral dimension corresponds to the width of the through-hole measured at the level of the first surface of the green body plate. In the case of a recess in the form of a depression or a groove, the lateral dimension corresponds to the width of the depression or groove measured at the level of the first surface of the green body plate. In the case of a recessed area extending around one or more island-like (island-shaped) non-recessed portions, the lateral dimension is the distance between the edges of adjacent portions measured at the level of the first surface of the green body plate.

[0076] The lateral dimension of the one or more recesses measured at the level of the first surface of the green body plate is preferably in the range of 11 μm to 5500 μm, preferably 50 μm to 5500 μm (in particular, in the case of through-holes). The lateral dimension of the recesses on the first surface of the green body plate prepared in step (i) is typically larger than the lateral dimension of the corresponding recesses on the first surface of the resulting gas-permeable electronically conductive plate due to the shrinkage occurring during sintering in step (iii) of the method defined above.

[0077] The thickness of the green body plate refers to the position without recesses and is understood to be determined at the position without recesses. Preferably, the green body plate prepared in step (i) has a thickness in the range of 45 μm to 3000 μm as measured at the position without recesses. The thickness of the green body plate prepared in step (i) is typically greater than the thickness of the resulting gas-permeable electronically conductive plate due to the shrinkage that occurs during sintering in step (iii) of the method defined above.

[0078] In a first embodiment of a method for preparing a gas-permeable electronically conductive plate, in step (i), the green body plate is obtained in its final shape (i.e., including one or more recesses extending in the thickness direction of the green body plate from the first surface as defined above) by forming a mixture comprising the metal particles and the polymer binder on the green body plate. Preferably, the mixture comprises the metal particles and the polymer binder. Preferably, the green body plate is formed by a technique selected from the group consisting of injection molding, molding, pressing, or 3D printing of a mixture comprising the metal particles and the polymer binder. Such techniques are known in the art.

[0079] In the case of 3D printing, the granules obtained by compounding metal particles with a liquid binder, a liquefied binder, or a solid binder are converted into 3D printing filaments by melt filament manufacturing. Such techniques are known in the art, for example, WO2017 / 009190A1, which describes filaments comprising a core material containing inorganic powder, the core material being coated with a layer of a shell material containing a thermoplastic polymer, and US2016 / 024293A1, which discloses the use in a method for manufacturing a melt filament of a mixture comprising 40 to 70% by volume (relative to the total amount of the mixture) of inorganic powder, 30 to 60% by volume (relative to the total amount of the mixture) of a binder (B) ((b1) at least one polyoxymethylene (POM) of 50 to 96% by mass relative to the total mass of the binder, (b2) at least one polyolefin (PO) of 1 to 35% by mass relative to the total mass of the binder (B), and (b3) at least one further polymer of 2 to 40% by mass relative to the total mass of the binder (B)).

[0080] Thus, in a first embodiment of the method defined above, step (i) is as follows (a) forming a mixture comprising the metal particles and the polymer binder on the green body plate, the green body plate being preferably formed by a technique selected from the group consisting of injection molding, press molding, die pressing, and 3D printing of the mixture comprising the metal particles and the polymer binder, the step including.

[0081] In a second embodiment of the method for preparing a gas-permeable electron-conductive plate, in step (i), a green body plate is obtained by forming a blank plate having a first surface and a second surface facing each other and a thickness dimension extending perpendicular to the first surface and the second surface, the first surface and the second surface of the blank plate having no recesses, and then converting the blank plate into the green body plate by forming one or more recesses extending in the thickness direction of the obtained green body plate from the first surface.

[0082] The blank plate has a first surface and a second surface facing each other, and a thickness dimension extending perpendicular to the first surface and the second surface, and the first surface and the second surface of the blank plate do not have recesses. The first surface and the second surface are the largest surfaces of the blank plate.

[0083] Preferably, the blank plate is formed by a technique selected from the group consisting of plate pressing, tape casting, and extrusion molding of a mixture containing the metal particles and the polymer binder. Such techniques are known in the art. In the case of tape casting, the mixture may be in the form of a slurry containing the metal particles and the polymer binder. In the case of extrusion molding, the mixture may be in the form of granules obtained by compounding the metal particles with a binder. Preferably, the mixture consists of the metal particles and the polymer binder.

[0084] To convert the blank plate into a desired green body plate (i.e., to provide one or more recesses extending in the thickness direction of the green body plate from the first surface as defined above), the recesses are preferably formed by a technique selected from the group consisting of embossing the first surface of the blank plate and needling the blank plate. Such techniques are known in the art. Embossing is preferred for forming recesses having a depth less than the thickness of the green body plate. Needling is preferred for forming through holes.

[0085] Therefore, in the second embodiment, step (i) is as follows: (b) including a step of forming a mixture containing the metal particles and the polymer binder on a blank plate having a first surface and a second surface facing each other and a thickness dimension extending perpendicular to the first surface and the second surface, wherein the first surface and the second surface of the blank plate have no recesses, and the blank plate is preferably formed by a technique selected from the group consisting of plate pressing, tape casting, and extrusion molding of a mixture containing the metal particles and the polymer binder, and then converting the blank plate into the green body plate by forming one or more recesses extending in the thickness direction of the obtained green body plate from the first surface, wherein the recesses are preferably formed by a technique selected from the group consisting of embossing the first surface of the blank plate and needling the blank plate.

[0086] Embossing is particularly preferred for forming the recess in the form of a depression. This is because forming a depression by embossing requires a smaller volume of material flow than forming a groove by embossing.

[0087] In a specific version of the second embodiment as defined above of the method for preparing a gas-permeable electronically conductive plate, a blank plate having the bilayer structure as defined above is formed, and then, from the first surface, one or more recesses in the form of depressions extending in the thickness direction of the resulting green body plate are formed by embossing to convert the blank plate into a green body plate, the depth of the depression extending over 80 to 100%, preferably 90 to 100%, of the thickness of the layer having a higher porosity and / or a higher average pore diameter configured to contact the bipolar plate. When the depth of the depression extends over 100% of the thickness of the layer having a higher porosity and / or a higher average pore diameter configured to contact the bipolar plate, the depth of the depression may further extend over at most 50%, preferably at most 10%, of the thickness of the adjacent layer having a lower porosity and / or a lower average pore diameter configured to contact the catalyst layer. Thus, when the depth of the depression extends over 100% of the thickness of the first layer, the depth of the depression may further extend over 0 to 50%, preferably 0 to 10%, of the thickness of the second layer. Limiting the depth of the depression in this way has the advantage of avoiding the over-densification of the porous structure near the second surface of the gas-permeable electronically conductive plate configured to contact the catalyst layer by embossing, or even avoiding the deformation of the second surface of the gas-permeable electronically conductive plate.

[0088] In step (ii), the green body plate prepared in step (i) is debound to obtain a brown body plate without impairing its integrity and mechanical stability. Debinding means removing at least a part of the binder from the green body plate. In step (ii), any suitable technique for debinding may be used. For example, step (ii) may include one or more of thermal debinding, catalytic debinding, and solvent-based debinding. Such debinding techniques are known in the art.

[0089] To remove at least a portion of the binder by catalytic debinding, the green body plate is preferably exposed to an atmosphere containing a gaseous acid. Suitable processes are described, for example, in US2009 / 0288739 and US5145900.

[0090] The debinding step (ii) is preferably carried out at a temperature below the melting temperature of the binder. Generally, debinding is carried out at a temperature in the range of 20 °C to 150 °C, and particularly preferably in the range of 100 °C to 140 °C. Preferably, the debinding step is carried out for a period of 0.1 hour to 24 hours, particularly preferably 0.5 hour to 12 hours. The time required for debinding depends on the temperature applied, the concentration of the acid in the treatment atmosphere, and the size of the green body plate.

[0091] Suitable acids for debinding are, for example, inorganic acids that are gaseous at room temperature or can be vaporized below the treatment temperature. Examples include hydrogen halides and nitric acid. Hydrogen halides are hydrogen fluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide. Suitable organic acids are those having a boiling point below 130 °C at atmospheric pressure, such as formic acid, acetic acid, or trifluoroacetic acid and mixtures thereof. Acids having a boiling point above 130 °C, such as methanesulfonic acid, can be used in the debinding step in a mixture with a lower boiling point acid and / or water. Preferred acids for process step (iii) are a mixture of nitric acid, a 10 mass% aqueous solution of oxalic acid, and 50 volume% methanesulfonic acid in water. Furthermore, BF3 and its adducts with inorganic ethers can be used as acids.

[0092] When using a carrier gas, generally, before contact with the green body plate, the carrier gas is passed through the acid to load the acid. The acid-loaded carrier gas is then heated to the temperature at which debinding is carried out. This temperature is advantageously higher than the loading temperature to avoid condensation of the acid. Preferably, the temperature at which debinding is carried out is at least 1 K, particularly preferably at least 5 K, and most preferably at least 10 K higher than the temperature at which the carrier gas is loaded with the acid.

[0093] It is preferable to mix an acid with a carrier gas by a metering device and heat the gas mixture to a temperature at which the acid can no longer condense. Preferably, the temperature is at least 1 K, particularly preferably at least 5 K, and most preferably at least 10 K higher than the sublimation and / or vaporization temperature of the acid and / or the carrier gas.

[0094] The carrier gas is generally any gas that is inert under the reaction conditions of the catalytic debinding process. According to the present invention, a preferred carrier gas is nitrogen. The removal of the binder may be carried out under reduced pressure.

[0095] In the case of a green body plate containing the preferred binder defined above, the catalytic debinding is preferably continued until the polyoxymethylene (POM) of the binder is removed to at least 80% by mass, preferably at least 90% by mass, particularly preferably at least 95% by mass, based on the total mass of the POM. This can be confirmed by monitoring the mass loss.

[0096] At the temperature of the catalytic debinding process, the metal powder contained in the green body plate can undergo chemical reactions and / or physical transitions. In particular, the particles of the metal powder can fuse together, undergo solid-state transitions, and / or chemical reactions with an acidic atmosphere or the carrier gas.

[0097] During the catalytic debinding process, the composition of the binder can change.

[0098] In step (iii), the brown body plate obtained in step (ii) is sintered in a non-oxidizing atmosphere or under vacuum to form a gas-permeable electronically conductive plate according to the first aspect defined above. By sintering, the binder content is further reduced, and the metal particles of the brown body plate are joined together to form a continuum in which the metal particles are held together substantially without any binder.

[0099] In step (iii), during sintering, the binder content is reduced to less than 5% by volume, preferably less than 2% by volume, particularly preferably less than 0.5% by volume, and most preferably less than 0.01% by volume of the resulting gas-permeable electronically conductive plate.

[0100] Preferably, in step (iii), sintering is carried out at a temperature in the range of 700 °C to 1300 °C.

[0101] The sintering step is preferably carried out at atmospheric pressure using an atmosphere of argon, nitrogen, hydrogen, or a mixture thereof. It is also possible to use reduced pressure or vacuum, for example, from about 10 kPa to about 80 kPa, preferably from about 20 kPa to about 50 kPa.

[0102] During sintering, the metal particles in the green plate can undergo chemical reactions and / or physical migrations. As a result, the composition, shape, and size of the metal particles contained in the green plate obtained in step (ii) may be different from those of the gas-permeable electronically conductive plate obtained after step (iii).

[0103] During sintering, the average pore diameter may increase.

[0104] The gas-permeable electronically conductive plate obtained by the method according to the fourth aspect defined above preferably has one or more of the preferred features defined above and / or is selected from the preferred embodiments defined above disclosed in the context of the first aspect.

[0105] The following examples further illustrate the present invention without limiting the scope of the present invention.

Examples

[0106] Figure 1 shows a gas-permeable electronically conductive plate for use as a porous transport layer of an electrolytic cell.

[0107] Figure 2 shows a first preferred embodiment of the gas-permeable electronically conductive plate according to the present invention.

[0108] Figures 3a - c show examples of a second preferred embodiment of a gas - permeable electronically - conductive plate according to the present invention.

[0109] Figure 3d shows another example of a second preferred embodiment of a gas - permeable electronically - conductive plate according to the present invention.

[0110] Figure 4 shows a building unit for an electrolytic cell.

[0111] Figure 5 shows a first preferred embodiment of a building unit for an electrolytic cell.

[0112] Figure 6 shows a second preferred embodiment of a building unit for an electrolytic cell.

[0113] Figures 7a and 7b show a flow diagram of an example of a first embodiment of a method for preparing a gas - permeable electronically - conductive plate.

[0114] Figure 8 shows a flow diagram of a second embodiment of a method for preparing a gas - permeable electronically - conductive plate.

[0115] The figures are schematic diagrams and are not drawn to scale.

[0116] Figure 1 shows a cross - section of a gas - permeable electronically - conductive plate 1 for use as a porous transport layer of an electrolytic cell. The gas - permeable electronically - conductive plate 1 includes one or more metal particles selected from the group consisting of titanium, titanium alloys, and stainless steel. The gas - permeable electronically - conductive plate 1 has a plurality of pores 4 having an average pore diameter. The gas - permeable electronically - conductive plate 1 has a first surface 2 and a second surface 3 facing each other, and a thickness dimension T extending perpendicular to the first surface 2 and the second surface 3. In the gas - permeable electronically - conductive plate 1 according to the present invention, the first surface 2 has one or more recesses (not shown in Figure 1) extending in the thickness direction T of the gas - permeable electronically - conductive plate 1 from the first surface 2. The recess has a lateral dimension d on the first surface 2 of the gas - permeable electronically - conductive plate that is larger than the average pore diameter of the pores.

[0117] A first preferred embodiment of the gas-permeable electronically conductive plate according to the present invention is shown in FIG. 2. The upper part of FIG. 2 is a cross-sectional view of the gas-permeable electronically conductive plate 11 having a first surface 12 and a second surface 13. The lower part of FIG. 2 is a plan view of the first surface 12 of the gas-permeable electronically conductive plate 11. The gas-permeable electronically conductive plate 11 has one or more recesses in the form of through-holes 15 extending from the first surface 12 to the second surface 13 of the gas-permeable electronically conductive plate 11. The through-hole 15 has a central axis extending perpendicularly from the first surface 12 to the second surface 13 of the gas-permeable electronically conductive plate 11. The through-hole 15 has a width at the level of the first surface 12 of the gas-permeable electronically conductive plate 11. The width of the through-hole 15 at the level of the first surface 12 of the gas-permeable electronically conductive plate 11 is larger than the average pore diameter of the pores 14 of the gas-permeable electronically conductive plate 11. Preferably, the width of the through-hole 15 at the level of the first surface 12 of the gas-permeable electronically conductive plate 11 is in the range of 20 μm to 1000 μm, preferably 40 μm to 800 μm, more preferably 50 μm to 600 μm. The through-hole 15 has a width that tapers in the direction from the first surface 12 to the second surface 13 of the gas-permeable electronically conductive plate 11 (as shown in the upper part of FIG. 2), and is preferably such that the loss at the contact interface with the catalyst layer on the second surface 13 of the gas-permeable electronically conductive plate 11 is reduced.

[0118] The through-hole 15 may have a circular contour (as shown in the lower part of FIG. 2), or an elliptical, square, polygonal, or any other suitable contour. Preferably, the diameter d of the circular through-hole 15 at the level of the first surface 12 of the gas-permeable electronically conductive plate 11 is in the range of 20 μm to 1000 μm, preferably 40 μm to 800 μm, more preferably 50 μm to 600 μm. The through-hole 15 has a diameter d that tapers in the direction from the first surface 12 to the second surface 13 of the gas-permeable electronically conductive plate 11 (as shown in the upper part of FIG. 2), and is preferably such that the loss at the contact interface with the catalyst layer on the second surface 13 of the gas-permeable electronically conductive plate 11 is reduced.

[0119] In a second preferred embodiment, the gas-permeable electronically conductive plate has one or more recesses having a depth less than the thickness of the plate at non-recessed positions, and there are no recesses having a depth equal to the thickness of the gas-permeable electronically conductive plate. Examples of such embodiments are shown in FIGS. 3a-3c. For clarity, in these figures, the porosity of each of the gas-permeable electronically conductive plates 21, 31, and 41 is not shown.

[0120] The upper part of FIG. 3a is a cross-sectional view of a gas-permeable electronically conductive plate 21 having a first surface 22 and a second surface 23. The lower part of FIG. 3a is a plan view of the first surface 22 of the gas-permeable electronically conductive plate 21. In the plan view, the non-recessed region is shown in black and the recessed region is shown in white. The gas-permeable electronically conductive plate 21 has one or more recesses in the form of depressions 25 having a depth D extending in the thickness direction T of the gas-permeable electronically conductive plate 21 from the first surface 22. The depth D of the depression 25 is less than the thickness T of the gas-permeable electronically conductive plate 21. The width of the depression 25 at the level of the first surface 22 of the gas-permeable electronically conductive plate 21 is larger than the average pore diameter of the pores (not shown in FIG. 3a) of the gas-permeable electronically conductive plate 21. Preferably, the width of the depression 25 is in the range of 10 μm to 5000 μm at the level of the first surface 22 of the gas-permeable electronically conductive plate 21.

[0121] The depression 25 may have a circular contour (as shown in the lower part of FIG. 3a), or an elliptical, square, polygonal, or any other suitable contour. Such a depression may have a U-shape (as shown in the upper part of FIG. 3a), a V-shape (triangle), a square, a semi-circular, or any other suitable cross-section. Preferably, the diameter d of the circular depression 25 is in the range of 10 μm to 5000 μm at the level of the first surface 22 of the gas-permeable electronically conductive plate 21. The depression 25 may have a U-shape (as shown in the upper part of FIG. 3a), a V-shape (triangle), a square, a semi-circular, or any other suitable cross-section. The second surface 23 of the gas-permeable electronically conductive plate 21 has no recesses.

[0122] The upper part of Fig. 3b is a cross-sectional view of a gas-permeable electronically conductive plate 31 having a first surface 32 and a second surface 33. The lower part of Fig. 3b is a plan view of the first surface 32 of the gas-permeable electronically conductive plate 31. In the plan view, the non-recessed regions are shown in black and the recessed regions are shown in white. The gas-permeable electronically conductive plate 31 has one or more recesses in the form of grooves 35 that extend in the thickness direction T of the gas-permeable electronically conductive plate 31 from the first surface 32. The depth D of the groove 35 is less than the thickness T of the gas-permeable electronically conductive plate 31. The width d of the groove 35 at the level of the first surface 32 of the gas-permeable electronically conductive plate 31 is greater than the average pore diameter of the pores (not shown in Fig. 3b) of the gas-permeable electronically conductive plate 31. Preferably, the groove 35 has a width d of 10 μm to 5000 μm at the level of the first surface 32 of the gas-permeable electronically conductive plate 31. The groove 35 may have a straight line (as shown in the lower part of Fig. 3b), a zigzag pattern, a zigzag, a serpentine, a honeycomb, or any other suitable path. The groove 35 may have a U-shape, a V-shape (triangle), a rectangular shape, a square shape (as shown in the upper part of Fig. 3b), a semi-circular shape, or any other suitable cross-section. The groove 35 may form a continuous channel extending from a fluid inlet to a fluid outlet. The second surface 33 of the gas-permeable electronically conductive plate 31 does not have a recess.

[0123] The upper part of Fig. 3c is a cross-sectional view of a gas-permeable electronically conductive plate 41 having a first surface 42 and a second surface 43. The lower part of Fig. 3c is a plan view of the first surface 42 of the gas-permeable electronically conductive plate 41. In the plan view, the non-recessed regions are shown in black and the recessed regions are shown in white. The gas-permeable electronically conductive plate 41 has a recessed region 45 extending around one or more island-like (island-shaped) non-recessed portions 46 on the first surface 42 of the gas-permeable electronically conductive plate 41. The depth D of the recessed region 45 is less than the thickness T of the gas-permeable electronically conductive plate 41. Each non-recessed portion 46 has a top surface at the level of the first surface 42 of the gas-permeable electronically conductive plate 41. The recessed region 45 surrounding the non-recessed portion 46 provides a passage for fluid flow around the non-recessed portion 46 that provides electrical contact with the bipolar plate. The lateral distance d between the edges of adjacent non-recessed portions 46 at the level of the first surface 42 of the gas-permeable electronically conductive plate 41 is greater than the average pore diameter of the pores (not shown in Fig. 3c) of the gas-permeable electronically conductive plate 41. Preferably, the lateral distance between the edges of adjacent non-recessed portions 46 of the first surface 42 is in the range of 20 μm to 5000 μm as measured at the level of the first surface. The island-like (island-shaped) non-recessed portions 46 may have the shape of ridges, dams, columns (as shown in Fig. 3c), posts, honeycombs, truncated pyramids, truncated cones, stepped structures (i.e., structures that taper towards the first surface of the gas-permeable electronically conductive plate 41), or any other suitable structure. Combinations of non-recessed portions 46 having different structures are also possible. The second surface 43 of the gas-permeable electronically conductive plate 41 does not have recesses.

[0124] The upper part of FIG. 3d is a cross-sectional view of a gas-permeable electronically conductive plate 51a having a first surface 52a and a second surface 53a. The gas-permeable electronically conductive plate 51a has a two-layer structure composed of a first layer 57a and a second layer 58a, and the first layer 57a has a higher porosity and / or a higher average pore diameter than the second layer 58a. The central part of FIG. 3d is a cross-sectional view of a gas-permeable electronically conductive plate 51b having a first surface 52b and a second surface 53b. The gas-permeable electronically conductive plate 51b has a two-layer structure composed of a first layer 57b and a second layer 58b, and the first layer 57b has a higher porosity and / or a higher average pore diameter than the second layer 58b. Each of the layers 57a and 57b is configured to contact a bipolar plate, and each of the layers 58a and 58b is configured to contact a catalyst layer.

[0125] The lower part of FIG. 3d is a plan view of the first surface 52a of the gas-permeable electronically conductive plate 51a and the first surface 52b of the gas-permeable electronically conductive plate 51b, respectively. In the plan view, the non-recessed regions are shown in black, and the recessed regions are shown in white.

[0126] The gas-permeable electronically conductive plate 51a has a plurality of recesses in the form of depressions 55a having a depth D extending in the thickness direction T of the gas-permeable electronically conductive plate 51a from the first surface 52a. The depth D of the depression 55a is less than the thickness direction T of the gas-permeable electronically conductive plate 51a, extends over 80 to 100% of the thickness of the layer 57a of the gas-permeable electronically conductive plate 51a, and does not reach the thickness of the layer 58a of the gas-permeable electronically conductive plate 51a (upper part of FIG. 3d). The depressions 55a are uniformly distributed on the first surface 52a of the gas-permeable electronically conductive plate 51a.

[0127] The gas-permeable and electronically conductive plate 51b has a plurality of recesses in the form of depressions 55b having a depth D extending in the thickness direction T of the gas-permeable and electronically conductive plate 51b from the first surface 52b. The depth D of the depression 55b is less than the thickness T of the gas-permeable and electronically conductive plate 51b, and extends over 100% of the thickness of the layer 57b of the gas-permeable and electronically conductive plate 51b and at most 50%, preferably at most 10%, of the thickness of the layer 58b (central part of FIG. 3d). The depressions 55b are uniformly distributed on the first surface 52b of the gas-permeable and electronically conductive plate 51b.

[0128] The width of the depression 55a at the level of the first surface 52a of the gas-permeable and electronically conductive plate 51a is larger than the average pore diameter of the pores of the layer 57a of the gas-permeable and electronically conductive plate 51a. The width of the depression 55b at the level of the first surface 52b of the gas-permeable and electronically conductive plate 51b is larger than the average pore diameter of the pores of the layer 57b of the gas-permeable and electronically conductive plate 51b.

[0129] Preferably, the width of each of the depressions 55a, 55b is in the range of 10 μm to 5000 μm at the level of the first surfaces 52a, 52b of the gas-permeable and electronically conductive plates 51a, 51b, respectively. Each of the depressions 55a, 55b may have a circular contour (as shown in the lower part of FIG. 3d), or an elliptical, square, polygonal, or any other suitable contour. The depressions 55a, 55b may have a U-shape (as shown in the upper and central parts of FIG. 3d), V-shape (triangle), square, semi-circular, or any other suitable cross-section. Preferably, the diameter d of each of the circular depressions 55a, 55b is in the range of 10 μm to 5000 μm at the level of the first surfaces 52a, 52b of the gas-permeable and electronically conductive plates 51a, 51b, respectively. The second surfaces 53a of the gas-permeable and electronically conductive plate 51a and the second surface 53b of the gas-permeable and electronically conductive plate 51b each do not have a recess.

[0130] FIG. 4 shows a cross-sectional view of a building unit for an electrolytic cell. The building unit is hereinafter - The gas-permeable electronically conductive plate 1 according to the first aspect defined above and - The gas-impermeable electronically conductive bipolar plate 20 in contact with the first surface 2 of the gas-permeable electronically conductive plate 1, and - The catalyst layer 30 in contact with the second surface 3 of the gas-permeable electronically conductive plate 1 comprise or consist of these.

[0131] As described above, in the building unit, hereinafter, - The gas-impermeable electronically conductive bipolar plate 20 in contact with the first surface 2 of the gas-permeable electronically conductive plate 1, and - The catalyst layer 30 in contact with the second surface 3 of the gas-permeable electronically conductive plate 1 at least one of must be present beside the gas-permeable electronically conductive plate 1.

[0132] In FIG. 4, the gas-permeable electronically conductive plate 1 is preferably according to any of the preferred embodiments shown in FIGS. 2 and 3a - c.

[0133] In FIG. 4, the catalyst layer 30 is an anode catalyst layer and contains a catalyst capable of catalyzing electrochemical oxygen generation. The catalyst is preferably selected from the group consisting of iridium, iridium oxide, platinum, platinum oxide, palladium, palladium oxide, ruthenium, ruthenium oxide, and mixtures of the oxides listed herein. The catalyst is non-supported or supported on a suitable catalyst support selected from the group consisting of, for example, SnO2, TiO2, and carbon black.

[0134] For illustrative purposes only, FIG. 4 also shows the proton exchange membrane 40 in contact with the anode catalyst layer 30 and the cathode catalyst layer 50 in contact with the proton exchange membrane 40. However, the proton exchange membrane 40 and the cathode catalyst layer 50 are not essential components of the building unit according to the second aspect defined above.

[0135] Figure 5 is a cross-sectional view showing a first preferred embodiment of a building unit for an electrolytic cell. The building unit is hereinafter - a gas-permeable electronically conductive plate 1, wherein the recess 5 on the first surface 2 of the gas-permeable electronically conductive plate 1 preferably has a lateral dimension in the range of 100 μm to 5000 μm, the gas-permeable electronically conductive plate 1; - a gas-impermeable electronically conductive bipolar plate 20 having a surface in contact with the first surface 2 of the gas-permeable electronically conductive plate 1, wherein the surface of the bipolar plate 20 in contact with the first surface 2 of the gas-permeable electronically conductive plate 1 has no recess, the gas-impermeable electronically conductive bipolar plate 20; comprises or consists of these.

[0136] In the embodiment shown in Figure 5, the bipolar plate 20 only provides an electronic contact between adjacent cells of the electrolytic cell and does not provide any fluid flow structure. Any reactant transport is carried out within the gas-permeable electronically conductive plate 1. To facilitate lateral reactant transport, the gas-permeable electronically conductive plate 1 preferably has at least one recess 5 in the form of a continuous channel or a continuous concave region extending around a plurality of island-like (island-shaped) non-recessed portions. Continuous means that the recess 5 extends from a fluid inlet connected to the fluid supply manifold of the electrolytic cell to a fluid outlet connected to the fluid removal manifold of the electrolytic cell. One or more recesses 5 on the first surface 2 of the gas-permeable electronically conductive plate 1 preferably have a lateral dimension (e.g., channel width d) in the range of 100 μm to 5000 μm. This dimension is in the same range as the lateral dimension (e.g., channel width) of the flow field structure of a state-of-the-art bipolar plate commonly used.

[0137] Figure 6 is a cross-sectional view showing a second preferred embodiment of a building unit for an electrolytic cell. The building unit is hereinafter - a gas-permeable electronically conductive plate 1; - A gas-impermeable electronically conductive bipolar plate 20 having a flow field surface in contact with the first surface 2 of the gas-permeable electronically conductive plate 1, comprising, or consisting of, The flow field surface of the bipolar plate 20 has a fluid flow structure including recesses 7 extending between protruding regions 8, and one or more of the protruding regions 8 extend across one or more of the recesses 5 on the first surface 2 of the gas-permeable electronically conductive plate 1. Preferably, the protruding regions 8 on the flow field surface of the bipolar plate 20 have a lateral dimension d', which is greater than the lateral dimension d of the recesses 5 on the first surface 2 of the gas-permeable electronically conductive plate 1.

[0138] In the embodiment shown in FIG. 6, the adjacent first surfaces 2 of the bipolar plate 20 and the gas-permeable electronically conductive plate 1 cooperate in providing a fluid flow structure for reactant transport.

[0139] The bipolar plate 20 has a flow field surface in contact with the first surface 2 of the gas-permeable electronically conductive plate 1. The first surface 2 of the gas-permeable electronically conductive plate 1 has one or more recesses 5 extending in the thickness direction T of the gas-permeable electronically conductive plate 1 from the first surface 2. The flow field surface of the bipolar plate 20 has a fluid flow structure including recesses 7 extending between protruding regions 8. Such a fluid flow structure is also referred to as a flow field. Suitable flow field designs are known in the art. Typically, the flow field includes at least one recess 7 forming a continuous channel extending between two protruding regions 8 providing the walls of the channel. Continuous means that the recess 7 extends from a fluid inlet connected to the fluid supply manifold of the electrolytic cell to a fluid outlet connected to the fluid removal manifold of the electrolytic cell.

[0140] In the building unit according to FIG. 6, one or more of the protruding regions 8 on the flow field surface of the bipolar plate 20 extend across one or more of the recesses 5 on the first surface 2 of the gas-permeable electronically conductive plate 1 adjacent to the flow field surface of the bipolar plate 20.

[0141] Preferably, as shown in FIG. 6, the protruding region 8 on the flow field surface of the bipolar plate 20 has a lateral dimension d' that is larger than the lateral dimension d of the recess 5 on the first surface 2 of the gas-permeable electronically conductive plate 1 adjacent to the flow field surface of the bipolar plate 20. The lateral dimension d' of the protruding region 8 on the flow field surface of the bipolar plate 20 is preferably in the range of 100 μm to 5000 μm, and the lateral dimension d of the recess 5 on the first surface 2 of the gas-permeable electronically conductive plate 1 is preferably in the range of 10 μm to 1000 μm.

[0142] FIG. 7a shows an example of a first embodiment of a method for manufacturing a gas-permeable electronically conductive plate starting from a powder mixture containing metal particles and a binder, or from granules obtained by compounding a binder and metal particles. In step (i), each of the powder mixture and the granules is formed into a green body plate, for example, by any of injection molding, press molding, and die pressing. In step (ii), the green body plate is debound to obtain a brown body plate. In step (iii), the brown body plate is sintered to form a gas-permeable electronically conductive plate.

[0143] FIG. 7b shows another example of a first embodiment of a method for preparing a gas-permeable electronically conductive plate starting from granules obtained by compounding a binder and metal particles. Granules obtained by compounding metal particles and a liquid binder or a liquefied binder or a solid binder are converted into 3D printing filaments by melt filament manufacturing. Such techniques are known in the art. In step (i), the granules or the filaments are formed into a green body plate by 3D printing. In step (ii), the green body plate is debound to obtain a brown body plate. In step (iii), the brown body plate is sintered to form a gas-permeable electronically conductive plate.

[0144] Figure 8 shows an example of a second embodiment of a method for preparing a gas-permeable electronically conductive plate starting from a powder mixture or slurry containing metal particles and a binder, or from granules obtained by compounding a binder and metal particles. In step (i), the mixture is formed into a blank plate, for example, by any of plate pressing of the powder mixture, tape casting of the slurry, and extrusion molding of the granules.

[0145] The blank plate has a first surface and a second surface facing each other and a thickness dimension extending perpendicular to the first surface and the second surface, and the first surface and the second surface of the blank plate have no recesses. Step (i) also includes converting the blank plate into a green body plate by forming one or more recesses extending in the thickness direction of the resulting green body plate from the first surface. The recesses are preferably formed by a technique selected from the group consisting of embossing the first surface of the blank plate and needling the blank plate. In step (ii), the green body plate is debound to obtain a brown body plate. In step (iii), the brown body plate is sintered to form a gas-permeable electronically conductive plate.

[0146] Preparation of a green body plate having different types of recesses on the first surface (step (i)) was carried out as follows: Example 1: Green body plate having a honeycomb pattern on the first surface Granules obtained by compounding titanium powder and a binder according to unpublished PCT application WO2023 / 061869 (titanium content in the range of 50 to 65% by volume) were hot pressed between two plates heated to a temperature of 165°C to form a blank plate having a thickness of 640 μm and a lateral dimension of about 10 cm × 10 cm. The thickness of the blank plate was controlled by a spacer placed between the two heated plates. The blank plate had a first surface and a second surface without recesses.

[0147] The conversion of the blank plate into the green body plate was carried out by embossing using a stainless - steel plate with a laser - generated pattern that forms a negative of the pattern formed on the first surface of the green body plate, thereby forming a honeycomb structure on the first surface of the plate. The embossing was carried out by a calendar (Saueressig GKL300L) with a fixed gap of 500 μm, applying a roll temperature of 150 °C and a pressure of 0.4 MPa.

[0148] The first surface of the obtained green body plate had a honeycomb pattern including island - like (island - shaped) hexagonal non - concave portions with a width of 4500 μm surrounded by concave regions having a width of 600 μm (distance between the edges of adjacent honeycombs) and a depth of about 140 μm.

[0149] Example 2: Green body plate having a columnar array on the first surface Granules obtained by compounding titanium powder and a binder according to unpublished PCT application WO2023 / 061869 (in the range of 50 - 65 vol% titanium content) were hot - pressed between two plates heated to a temperature of 165 °C to form a blank plate having a thickness of 640 μm and a lateral dimension of about 10 cm×10 cm. The thickness of the blank plate was controlled by spacers placed between the two heated plates. The blank plate had a first surface and a second surface without recesses.

[0150] The conversion of the blank plate into the green body plate was carried out by embossing using a stainless - steel plate with a laser - generated pattern that forms a negative of the pattern formed on the first surface of the green body plate, thereby forming a columnar array on the first surface of the plate. The embossing was carried out by a calendar (Saueressig GKL300L) with a fixed gap of 500 μm, applying a roll temperature of 150 °C and a pressure of 0.4 MPa.

[0151] The first surface of the obtained green body plate had a columnar arrangement including non-recessed portions in the shape of islands (island-shaped columns) with a diameter of approximately 600 μm surrounded by a recessed region having a width of approximately 400 μm (distance between the edges of adjacent columns) and a depth of approximately 180 μm.

[0152] Example 3: Green body plate having a columnar arrangement on the first surface Granules obtained by compounding titanium powder and a binder according to unpublished PCT application WO2023 / 061869 (titanium content in the range of 50 to 65% by volume) were hot-pressed between two plates heated to a temperature of 165 °C to form a blank plate having a thickness of 640 μm and lateral dimensions of approximately 10 cm × 10 cm. The thickness of the blank plate was controlled by spacers placed between the two heating plates. The blank plate had a first surface and a second surface without recesses.

[0153] The conversion of the blank plate into a green body plate was carried out by embossing with a calendar (Saueressig GKL300L) at a roll temperature of 150 °C, a fixed gap of 500 μm, and applying a pressure of 4 MPa using a stainless steel plate having a laser pattern with a thickness of 200 μm (provided with a pattern forming a negative of the pattern to be formed on the first surface of the green body plate) to form a columnar arrangement on the first surface of the plate.

[0154] The first surface of the obtained green body plate had a columnar arrangement including non-recessed portions in the shape of islands (island-shaped columns) with a diameter of approximately 200 μm surrounded by a recessed region having a width of approximately 200 μm (distance between the edges of adjacent columns) and a depth of approximately 80 μm.

[0155] Example 4: Green body plate having channels parallel to the first surface Granules obtained by compounding titanium powder and a binder according to unpublished PCT application WO2023 / 061869 (in the range of 50 to 65% by volume of titanium content) were hot-pressed between two plates heated to a temperature of 165 °C to form a blank plate having a thickness of 640 μm and a lateral dimension of about 10 cm × 10 cm. The thickness of the blank plate was controlled by a spacer placed between the two heating plates. The blank plate had a first surface and a second surface without recesses.

[0156] The conversion of the blank plate into a green body plate was carried out by embossing using a stainless-steel plate with a laser-generated pattern that forms a negative of the pattern formed on the first surface of the green body plate, thereby forming channels parallel to the first surface of the plate. The embossing was carried out by a calendar (Saueressig GKL300L) with a fixed gap of 500 μm, applying a roll temperature of 150 °C and a pressure of 4 MPa.

[0157] The first surface of the obtained green body plate had recesses in the form of parallel channels having a V-shaped cross-section with a width of 0.1 mm and a depth of about 80 μm measured at the level of the first surface. The thickness of the wall between the channels measured at the level of the deepest point of the channels was about 200 μm.

[0158] Example 5: Green body plate having channels parallel to the first surface Granules obtained by compounding titanium powder and a binder according to unpublished PCT application WO2023 / 061869 (in the range of 50 to 65% by volume of titanium content) were hot-pressed between two plates heated to a temperature of 165 °C to form a blank plate having a thickness of 640 μm and a lateral dimension of about 10 cm × 10 cm. The thickness of the blank plate was controlled by a spacer placed between the two heating plates. The blank plate had a first surface and a second surface without recesses.

[0159] The conversion of the blank plate into the green body plate was carried out by embossing using a stainless-steel plate with a laser-generated pattern that forms a negative of the pattern formed on the first surface of the green body plate, thereby forming channels parallel to the first surface of the plate. The embossing was carried out by a calendar (Saueressig GKL300L) with a fixed gap of 500 μm applying a roll temperature of 150 °C and a pressure of 4 MPa.

[0160] The first surface of the obtained green body plate had recesses in the form of parallel channels having a U-shaped cross-section with a width of 100 μm and a depth of about 180 μm measured at the level of the first surface. The thickness of the wall between the channels measured at the level of the deepest point of the channels was about 300 μm.

[0161] The green body plate obtained according to any of Examples 1 to 7 was debound (step (ii)) to obtain a brown body plate, and the obtained brown body plate was sintered in a non-oxidizing atmosphere or under vacuum (step (iii)) to form a gas-permeable electronically conductive plate for use as the porous transport layer of the electrolytic cell.

[0162] Example 6: Green body plate having a recess arrangement and a two-layer structure on the first surface By co-extruding equal amounts of the first and second granules obtained by compounding titanium powder and a binder according to the unpublished PCT application WO2023 / 061869, a blank plate having a total thickness of 420 μm and a lateral dimension of about 10 cm × 10 cm was obtained. The titanium content of the first granules ranged from 50 to 65% by volume, the titanium content of the second granules ranged from 65 to 85% by volume, and the titanium content of the second granules was selected to be higher than that of the first granules. The obtained blank plate had a first surface and a second surface without recesses and included two layers of equal thickness (210 μm in each case) with different titanium / binder ratios.

[0163] The conversion of the blank plate into the green body plate was carried out by embossing with a calendar (Saueressig GKL300L) at a roll temperature of 150 °C and a fixed gap of 500 μm while applying a pressure of 4 MPa, using an etched stainless steel plate with a thickness of 500 μm (provided with a pattern forming the negative of the pattern formed on the first surface of the green body plate), thereby forming a recess array on the first surface of the plate.

[0164] The first surface of the obtained green body plate had an array including concave portions in the shape of recesses having a diameter of approximately 300 μm and a depth of approximately 300 μm, and the distance between the edges of adjacent recesses was about 300 μm.

[0165] Example 7: Green body plate having a recess array and a two-layer structure on the first surface By co-extruding different amounts of the first and second granules obtained by compounding titanium powder and a binder according to unpublished PCT application WO2023 / 061869, a blank plate having a total thickness of 420 μm and a lateral dimension of about 10 cm × 10 cm was obtained. The titanium content of the first granules was in the range of 50 - 65 vol%, the titanium content of the second granules was in the range of 65 - 85 vol%, and the titanium content of the second granules was selected to be higher than that of the first granules. The obtained blank plate had a first surface and a second surface without recesses, and included two layers with different titanium / binder ratios and different thicknesses (first layer obtained from the first granules: 260 μm, second layer obtained from the second granules: 160 μm).

[0166] The conversion of the blank plate into the green body plate was carried out by embossing with a calendar (Saueressig GKL300L) at a roll temperature of 150 °C and a fixed gap of 500 μm while applying a pressure of 4 MPa, using an etched stainless steel plate with a thickness of 500 μm (provided with a pattern forming the negative of the pattern formed on the first surface of the green body plate), thereby forming a recess array on the first surface of the plate.

[0167] The first surface of the obtained green body plate had an array including concave portions in a recessed shape having a diameter of approximately 300 μm and a depth of approximately 300 μm, and the distance between the edges of adjacent recesses was about 300 μm.

[0168] Example 8: Green body plate having a recess array and a two-layer structure on the first surface Granules (titanium content in the range of 50 to 85% by volume) obtained by compounding titanium powder and a binder according to unpublished PCT application WO2023 / 06186 were hot-pressed between two plates heated to a temperature of 165 °C to form a blank plate having a thickness of 420 μm and a lateral dimension of about 10 cm × 10 cm. The thickness of the blank plate was controlled by a spacer disposed between the two heating plates. The blank plate had a first surface and a second surface without recesses.

[0169] The conversion of the blank plate into a green body plate was performed by embossing using a calendar (Saueressig GKL300L) at a roll temperature of 150 °C and a fixed gap of 500 μm with a pressure of 4 MPa, using an etched stainless steel plate with a thickness of 500 μm (provided with a pattern forming a negative of the pattern formed on the first surface of the green body plate), to form a recess array on the first surface of the plate.

[0170] The first surface of the obtained green body plate had a recess array including recessed portions in a recessed shape having a diameter of approximately 300 μm and a depth of approximately 300 μm, and the distance between the edges of adjacent recesses was about 300 μm.

Claims

1. A gas-permeable electron-conducting plate (51a, 51b) for use as a porous transport layer in an electrolytic cell, - Containing one or more metal particles selected from the group consisting of titanium, titanium alloys, and stainless steel, - Having multiple pores (14) with an average pore diameter, - It has a first surface (52a, 52b) and a second surface (53a, 53b) that face each other, and a thickness dimension (T) that extends perpendicularly to the first surface (52a, 52b) and the second surface (53a, 53b), The first surface (52a, 52b) of the gas-permeable electron-conductive plate (51a, 51b) has one or more recesses (55b) extending from the first surface (52a, 52b) in the thickness (T) direction of the gas-permeable electron-conductive plate (51a, 51b), The recess (55b) on the first surface (52a, 52b) of the gas-permeable electron-conductive plate (51a, 51b) has a lateral dimension (d) that is larger than the average pore diameter of the pore (14), One or more recesses (55b) have a depth (D) less than the thickness (T) of the gas-permeable electron-conductive plates (51a, 51b) in the non-recessed positions, and one or more of the recesses (55b) are in the form of indentations. The gas-permeable electron-conductive plate (51a, 51b) consists of a first layer (57a, 57b) and a second layer (58a, 58b), wherein the first layer (57a, 57b) has a higher porosity and / or a higher average pore size than the second layer (58a, 58b). The depth (D) of the recess (55b) extends over 100% of the thickness of the first layer (57b), and further extends over at most 50% of the thickness of the second layer (58b). Gas-permeable electron-conducting plates (51a, 51b).

2. The gas-permeable electron-conductive plate (51a, 51b) further has one or more recesses in the form of through holes (15) extending from the first surface (52a, 52b) to the second surface (53a, 53b), wherein the through holes (14) are as follows: - A central axis extending perpendicularly from the first surface (52a, 52b) to the second surface (53a, 53b), - The diameter (d) in the range of 20 μm to 1000 μm on the first surface and A gas-permeable electron-conducting plate (51a, 51b) according to claim 1, having the above.

3. The gas-permeable electron-conductive plates (51a, 51b) according to claim 1, wherein there are no recesses having a depth equal to the thickness (T) of the gas-permeable electron-conductive plates (51a, 51b).

4. The gas-permeable electron-conductive plate (51a, 51b) according to claim 1, 2, or 3, wherein the depth (d) of the recess is in the range of 10 μm to 5000 μm on the first surface (52a, 52b).

5. The aforementioned plate, - Thickness (T) measured in a location without recesses, in the range of 20 μm to 2000 μm. and / or - Porosity measured by volume injection mercury porosimetry in accordance with DIN 66133, in the range of 10% to 80% by volume, preferably 30% to 60% by volume. and / or - Average pore diameter in the range of 5 μm to 40 μm, measured by volume injection mercury porosimetry in accordance with DIN 66133. A gas-permeable electron-conducting plate (51a, 51b) according to claim 1, 2, or 3, having the above.

6. The gas permeable electron conductive plate according to claim 1, 2, or 3, wherein all recesses are in the form of indentations, and the indentations are uniformly distributed on the first surface of the gas permeable electron conductive plate.

7. A building unit for an electrolytic cell, and below, - A gas-permeable electron-conducting plate (1) as defined in claim 1, - and at least one of the following - A gas-impermeable, electron-conductive bipolar plate (20) in contact with the first surface (2) of the gas-permeable, electron-conductive plate (1), and - A catalyst layer (30) in contact with the second surface (3) of the gas-permeable electron-conductive plate (1), preferably comprising a catalyst capable of catalyzing an electrochemical oxygen evolution reaction. including, Building unit.

8. - A gas-permeable electron-conductive plate (1) according to claim 1, 2, or 3, wherein the recess (5) of the first surface (2) of the gas-permeable electron-conductive plate (5) preferably has a lateral dimension (d) in the range of 100 μm to 5000 μm, - A gas-impermeable electron-conductive bipolar plate (20) having a surface in contact with the first surface (2) of the gas-permeable electron-conductive plate (1), wherein the surface of the bipolar plate (20) in contact with the first surface (2) of the gas-permeable electron-conductive plate (1) does not have a recess. The building unit according to claim 7, including the following:

9. A building unit according to claim 7, the following: - A gas-permeable electron-conductive plate (1) according to claim 1, 2, or 3, - A gas-impermeable electron-conductive bipolar plate (20) having a flow field surface in contact with the first surface of the gas-permeable electron-conductive plate, Includes, The flow field surface of the bipolar plate (20) has a fluid flow structure including recesses (7) extending between protruding regions (8), and one or more of the protruding regions (8) extend across one or more of the recesses (5) of the first surface (2) of the gas-permeable electron-conducting plate (1). Preferably, the protruding region (8) on the flow field surface of the bipolar plate (20) has a lateral dimension (d'), and this lateral dimension (d') is greater than the lateral dimension (d) of the recess (5) on the first surface (2) of the gas-permeable electron-conductive plate (1). Building unit.

10. - Gas-permeable electron-conducting plates (51a, 51b) as defined in claim 1, 2, or 3, or - Building unit as defined in claim 7 An electrolytic cell comprising, Preferably, an electrolytic cell for the electrolysis of water, comprising an electrolyte in the form of a proton exchange membrane.

11. A method for preparing a gas-permeable electron-conductive plate (51a, 51b) as defined in claim 1, 2, or 3, comprising the following steps: (i) A step of forming a mixture comprising one or more metal particles selected from the group consisting of titanium, titanium alloys and stainless steel, and a polymer binder, to obtain a green plate, The green plate has a first surface and a second surface that face each other, and a thickness dimension that extends perpendicular to the first surface and the second surface. The first surface of the green body plate has one or more recesses extending from the first surface in the thickness direction of the green body plate, The average particle size of the metal particles changes in steps along the thickness dimension of the green plate, resulting in a two-layer structure, and the average particle size of the metal particles decreases along the thickness in the direction from the first surface to the second surface of the green plate. and / or The volume ratio between the metal particles and the binder changes stepwise along the thickness dimension of the green plate, resulting in a two-layer structure, and the volume ratio between the metal particles and the binder increases along the thickness in the direction from the first surface to the second surface of the green plate. One or more recesses have a depth less than the thickness of the green plate at the non-recessed location, and one or more of the recesses are in the form of a depression. The recess has a lateral dimension of preferably 11 μm to 5500 μm on the first surface of the green plate. process, (ii) A step of debinding the green body plate prepared in step (i) to obtain a brown body plate, (iii) A step of sintering the Brownian plate obtained in step (ii) in a non-oxidizing atmosphere or under vacuum to form the gas-permeable electron-conducting plate. Methods that include...

12. The method according to claim 11, wherein the metal particles have an average particle size of 15 μm to 106 μm as measured by laser diffraction.

13. A method according to claim 11, wherein step (i) is (a) A step of forming a mixture comprising the metal particles and the polymer binder on the green plate, wherein the green plate is preferably formed by a technique selected from the group consisting of injection molding, press molding, embossing, and 3D printing of the mixture comprising the metal particles and the polymer binder. or (b) The process includes forming a mixture comprising the metal particles and the polymer binder into a blank plate having a first surface and a second surface facing each other, and a thickness dimension extending perpendicular to the first surface and the second surface, wherein the first surface and the second surface of the blank plate have no recesses, and the blank plate is preferably formed by a technique selected from the group consisting of plate pressing, tape casting, and extrusion molding of the mixture comprising the metal particles and the polymer binder. The process then involves transforming the blank plate into the green plate by forming one or more recesses extending in the thickness direction of the resulting green plate from the first surface, wherein the recesses are formed by a technique selected from the group consisting of embossing the first surface of the blank plate. Methods that include...

14. The method according to claim 11, - Step (ii) includes one or more of the following: thermal debinding, catalytic debinding, and solvent debinding. and / or - In process (iii), sintering is performed at a temperature in the range of 700°C to 1300°C. method.

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