Water electrolysis cell, and method for manufacturing water electrolysis cell

Abstract

To provide a technique capable of suppressing degradation of members of a water electrolysis cell and helping it stably perform water electrolysis.SOLUTION: The water electrolysis cell comprises a bipolar plate, a diffusion layer diffusing water, a plate-shaped current collecting plate for water electrolysis which is formed separate from the bipolar plate, is disposed between the bipolar plate and the diffusion layer, and includes an electroconductive metallic material, with protrusions formed on one main face thereof and recesses formed on the other main face thereof on a portion on the opposite side of a portion where the protrusion is formed on the one main face. The current collecting plate for water electrolysis having a tip of each of the protrusions contacting the diffusion layer, is formed to allow water to flow inside the recesses thereof, and prevents gas flowing on the main face side from moving to the inside of the recesses.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a water electrolysis cell and a method for producing a water electrolysis cell. [Background technology]

[0002] Conventionally, water electrolysis cells that electrolyze water to produce hydrogen gas and oxygen gas have been known (for example, Patent Document 1). In general, in a water electrolysis cell, water to be electrolyzed flows through a flow path formed in a bipolar plate. This bipolar plate is electrically connected to an electrode, and supplies power to the electrode for electrolyzing water. For this reason, current is concentrated at the contact point between the bipolar plate and the electrode, which is likely to generate heat. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-12994 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the temperature of a component rises due to heat generation at the contact points between the bipolar plates and the electrodes, it may be cooled using water flowing through a flow path. However, because some of the water flowing through the flow path is electrolyzed, the flow rate gradually decreases as it flows through the flow path. Furthermore, because the water flowing through the flow path contains oxygen gas generated by electrolysis, the amount of water per unit volume of the flow path further decreases. For this reason, it is difficult to sufficiently cool the heat-generating areas with the water flowing through the flow path, and heat spots occur where the temperature rises locally, which may cause deterioration of the component.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a technique for suppressing deterioration of components in a water electrolysis cell and stably performing water electrolysis. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0007] (1) According to one aspect of the present invention, there is provided a water electrolysis cell comprising: a bipolar plate, a diffusion layer that diffuses water, and a plate-shaped current collector for water electrolysis that is formed separately from the bipolar plate and is disposed between the bipolar plate and the diffusion layer, the current collector for water electrolysis containing a conductive metal material and having a convex portion formed on one main surface and a concave portion formed on the other main surface opposite to the portion on the one main surface where the convex portion is formed, the current collector for water electrolysis being formed such that tips of the convex portions come into contact with the diffusion layer and water can flow inside the concave portions, and the current collector for water electrolysis is formed to restrict the movement of gas flowing on the one main surface side to the inside of the concave portions.

[0008] According to this configuration, the tips of the protrusions formed on one main surface of the plate-shaped current collector for water electrolysis are in contact with the diffusion layer, and current flows from the bipolar plate to the diffusion layer via the current collector for water electrolysis. As a result, current concentrates at the contact points between the tips of the protrusions and the diffusion layer, which makes the temperature rise easily and tends to form heat spots. In the above-mentioned configuration, the current collector for water electrolysis has recesses through which water can flow formed on the other main surface of the current collector for water electrolysis, on the side opposite the part where the protrusions are formed on one main surface. As a result, the contact points between the tips of the protrusions and the diffusion layer can be efficiently cooled by water flowing inside the recesses. Furthermore, the current collector for water electrolysis has a flow path on the one main surface side. The recesses are formed so as to restrict the movement of the gas passing through them to the inside of the recesses. Since oxygen gas is generated by electrolysis of water on one of the main surfaces, the amount of oxygen gas contained in the water flowing along one of the main surfaces increases as it moves downstream, resulting in a decrease in cooling efficiency. On the other hand, the water flowing along the other main surface does not contain oxygen gas even downstream, so cooling efficiency is maintained and the contact area between the tip of the protrusion and the diffusion layer can be cooled. Therefore, the occurrence of heat spots in the water electrolysis cell can be suppressed, which suppresses deterioration of the components and enables stable water electrolysis.

[0009] (2) In the water electrolysis cell of the above embodiment, the convex portions of the current collector plate for water electrolysis may extend along a first direction on the one main surface, and may be arranged in a plurality of rows in a direction intersecting the first direction. With this configuration, the portions where the temperature is likely to increase due to contact between the tips of the convex portions and the diffusion layer are distributed relatively evenly on the contact surface between the current collector plate for water electrolysis and the diffusion layer, so that local temperature increases can be suppressed. Furthermore, the concave portions through which water flows for efficiently cooling the contact portions between the tips of the convex portions and the diffusion layer are also formed on the opposite side of the one main surface to the portions where the convex portions are formed, so that the concave portions are arranged relatively evenly on the contact surface between the current collector plate for water electrolysis and the diffusion layer, and the contact portions between the tips of the convex portions and the diffusion layer can be cooled. Therefore, the occurrence of heat spots can be suppressed, and water electrolysis can be stably performed.

[0010] (3) In the water electrolysis cell of the above embodiment, the current collector plate for water electrolysis may be disposed between the bipolar plate and the diffusion layer, and the distance between the tips of two adjacent protrusions may be 1 mm or less, and the height of the protrusions may be 0.6 mm or less. According to this configuration, since the distance between the tips of two adjacent protrusions is relatively small, the flow of water on one main surface side is likely to be turbulent. This is also true for the recess formed on the opposite side of the protrusions. As a result, the flow of water on one main surface side of the current collector plate for water electrolysis is turbulent, so that even if oxygen gas is contained in the water as the electrolysis of water progresses, the water can be easily supplied to the diffusion layer. In addition, the flow of water on the other main surface side of the current collector plate for water electrolysis is turbulent, so that the cooling effect of water can be improved. Furthermore, according to the above configuration, the height of the protrusions is on the same scale as the distance between the tips of two adjacent protrusions, and is relatively deep as a flow path through which water flows. As a result, the pressure loss can be reduced on each of the one main surface side and the other main surface side, and therefore the energy required to flow water can be reduced. Therefore, the energy required for electrolyzing water in the water electrolysis cell can be reduced while the occurrence of heat spots can be suppressed, so that water can be electrolyzed stably.

[0011] (4) In the water electrolysis cell of the above embodiment, the current collector for water electrolysis may have a plurality of the convex portions formed on the one main surface of the current collector for water electrolysis. According to this configuration, the plurality of convex portions formed on the one main surface of the current collector for water electrolysis have a substantially cylindrical shape. Here, the "circle" as the cross-sectional shape of the "substantially cylindrical shape" is not limited to a perfect circle, but also includes those that appear to be circular or elliptical. Water flowing along the one main surface collides with the convex portions by flowing between the plurality of convex portions, and the direction of the flow changes. As a result, the flow of water on the one main surface side of the current collector for water electrolysis is disturbed, so that even if oxygen gas is contained in the water as the electrolysis of the water progresses, the water can be easily supplied to the diffusion layer. In addition, even on the other main surface side on which a plurality of recesses of a substantially cylindrical shape are formed, the flow of water flowing along the other main surface is disturbed, so that the cooling effect of the water can be improved. Therefore, the occurrence of heat spots can be suppressed, and the electrolysis of water can be stably performed.

[0012] (5) In the water electrolysis cell of the above aspect, the thickness of the current collector for water electrolysis may be 0.2 mm or less. With this configuration, the thickness of the current collector for water electrolysis is relatively small, and therefore the heat capacity is small. This allows the temperature to increase in a relatively short time at the start of the water electrolysis cell. Therefore, water electrolysis can be performed quickly and stably. Furthermore, even if the temperature rises due to current concentration at the contact points between the tips of the protrusions and the diffusion layer, the small heat capacity makes it easy to cool them down by the water flowing through the recesses. This allows the temperatures of the water electrolysis current collector plate and the diffusion layer to be quickly lowered, thereby suppressing the occurrence of heat spots. Therefore, water electrolysis can be performed stably.

[0013] (6) According to another aspect of the present invention, there is provided a method for manufacturing a water electrolysis cell. The method for manufacturing a water electrolysis cell includes a processing step of forming a convex portion on one main surface of a plate-shaped member containing a conductive metal material by cold working, and forming a concave portion on a portion of the other main surface opposite to the portion where the convex portion is formed on the one main surface, to form a current collector for water electrolysis, and a disposing step of disposing the current collector for water electrolysis between a bipolar plate and a diffusion layer. According to this configuration, the current collector for water electrolysis is formed with the convex portion and the concave portion by cold working, which is bending the member without applying heat. As a result, a heating step is not required, and therefore no heating equipment is required, and the current collector can be processed in a relatively short time. In addition, since no unnecessary material is discharged during processing, the material can be used more effectively than in cutting processing. Furthermore, in the current collector for water electrolysis processed in this manner, the contact portion between the tip of the convex portion and the diffusion layer can be efficiently cooled by water flowing inside the concave portion, and thus the occurrence of a heat spot can be suppressed. Therefore, the electrolysis of water can be stably performed.

[0014] The present invention can be realized in various forms, such as a current collector plate for water electrolysis, a method for manufacturing a current collector plate for water electrolysis, a method for laminating members when manufacturing a water electrolysis cell, a water electrolysis device including a water electrolysis cell, a water electrolysis system including a water electrolysis device, a control method for the water electrolysis device or the water electrolysis system, and a computer program for a controller to control the water electrolysis device or the water electrolysis system. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a water electrolysis system including a water electrolysis device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram of a water electrolysis cell included in the water electrolysis device. [Diagram 3] FIG. 1 is a diagram showing a schematic configuration of a water electrolysis device. [Figure 4] FIG. 2 is a diagram illustrating the arrangement of flow paths in a water electrolysis device. [Diagram 5] FIG. 2 is a perspective view of an anode-side spacer. [Figure 6] FIG. 2 is a perspective view of a current collector plate for water electrolysis. [Figure 7] FIG. 2 is a diagram illustrating the operation of a water electrolysis cell. [Figure 8] FIG. 2 is a diagram illustrating the function of a current collector plate for water electrolysis. [Figure 9] FIG. 2 is a diagram illustrating the operation of the water electrolysis cell of the first comparative example. [Figure 10] FIG. 4 is a schematic diagram of a water electrolysis system according to a second comparative example. [Figure 11] FIG. 11 is a diagram showing the results of a first evaluation test. [Figure 12] FIG. 13 is a diagram showing the results of a second evaluation test. [Figure 13] FIG. 4 is a schematic diagram of a current collector plate for water electrolysis according to a second embodiment. [Figure 14] FIG. 11 is a schematic diagram of a current collector plate for water electrolysis according to a third embodiment. [Figure 15] FIG. 13 is a schematic diagram of a current collector plate for water electrolysis according to a fourth embodiment. [Figure 16] FIG. 13 is a perspective view of a current collector plate for water electrolysis according to a fifth embodiment. [Figure 17] FIG. 2 is a cross-sectional view of a current collector plate for water electrolysis. [Figure 18] FIG. 13 is a schematic diagram of an anode side spacer according to a sixth embodiment. [Figure 19] 11A and 11B are diagrams illustrating the effect of changing the position of the manifold portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] First Embodiment 1 is a schematic diagram of a water electrolysis system 100 including a water electrolysis device 101 according to a first embodiment. The water electrolysis system 100 of this embodiment produces hydrogen gas and oxygen gas by electrolyzing water. The water electrolysis system 100 includes a water electrolysis apparatus 101, a DC power supply 102, two gas-liquid separators 103a and 103b, a heat exchanger 104, a water purifier 105, a dehumidifier 106, a pure water storage tank 107, a supply pump 108, and the like.

[0017] The water electrolysis apparatus 101 includes a plurality of water electrolysis cells, and is connected to a pure water storage tank 107 and a DC power supply 102. The water electrolysis apparatus 101 electrolyzes pure water supplied from the pure water storage tank 107 using power supplied from the DC power supply 102, to generate oxygen gas and hydrogen gas. A detailed configuration of the water electrolysis apparatus 101 will be described later.

[0018] Water containing oxygen gas generated in the water electrolysis device 101 is separated into oxygen gas and water in the gas-liquid separator 103a. The oxygen gas separated in the gas-liquid separator 103a is sent to a supply destination outside the water electrolysis system 100. The water from which the oxygen gas has been separated in the gas-liquid separator 103a is cooled in the heat exchanger 104 together with pure water supplied from a pure water storage tank 107 via a supply pump 108, and then sent to the water purifier 105 by the circulation pump 100a. The water from which impurities have been removed in the water purifier 105 is supplied to the water electrolysis device 101 and used again for electrolysis. Water containing hydrogen gas generated in the water electrolysis device 101 is separated into hydrogen gas and water in the gas-liquid separator 103b. The hydrogen gas separated in the gas-liquid separator 103b is sent to a supply destination outside the water electrolysis system 100. The water separated from the hydrogen gas in the gas-liquid separator 103b is sent to the water electrolysis device 101 by the circulation pump 100b.

[0019] FIG. 2 is a schematic diagram of a water electrolysis cell 1 included in the water electrolysis apparatus 101. FIG. 3 is a diagram showing a schematic configuration of the water electrolysis apparatus 101. FIG. 4 is a diagram explaining the arrangement of flow paths in the water electrolysis apparatus 101. The water electrolysis cell 1 shown in FIG. 2 is a solid polymer water electrolysis cell, and a plurality of the cells are stacked to form the solid polymer water electrolysis apparatus 101 shown in FIG. 1. The water electrolysis apparatus 101 is a so-called water electrolysis stack, and in this embodiment, it is formed by stacking four water electrolysis cells 1 (see FIG. 3). However, the number of water electrolysis cells 1 stacked in one water electrolysis apparatus 101 is not limited to this. In FIGS. 2 to 4, the direction in which the water electrolysis cells 1 are stacked is defined as the z-axis direction, and two directions perpendicular to the z-axis on a plane perpendicular to the z-axis are defined as the x-axis direction and the y-axis direction. For convenience of explanation, the thicknesses and sizes of the members constituting the water electrolysis cell 1 and the water electrolysis apparatus 101 shown in FIGS. 2 to 4 are different from the actual thicknesses and sizes.

[0020] The water electrolysis cell 1 includes a bipolar plate 10, an anode spacer 20, a membrane electrode joint 30, a cathode spacer 40, and a plurality of gaskets (not shown). In the water electrolysis cell 1, the bipolar plate 10, the gasket, the anode spacer 20, the gasket, the membrane electrode joint 30, the gasket, the cathode spacer 40, and the gasket are stacked in this order from the negative side in the z-axis direction. In this embodiment, the water electrolysis cell 1 has a rectangular parallelepiped shape, and a water electrolysis device 101 in which four water electrolysis cells 1 and one bipolar plate 10 are stacked has through holes 1a, 1b, 1c, and 1d formed at each of the four corners thereof, which penetrate the water electrolysis device 101 in the z-axis direction (see FIG. 4). The through holes 1a, 1b, 1c, and 1d serve as flow paths through which fluids involved in the electrolysis of water in each of the water electrolysis cells 1 included in the water electrolysis device 101 flow.

[0021] The bipolar plate 10 is a substantially rectangular plate-like member and serves as a separator disposed between adjacent water electrolysis cells 1. The bipolar plate 10 has a flow path 11 through which water supplied to the anode spacer 20 flows. The flow path 11 is formed at a corner of the bipolar plate 10 on the negative side in the x-axis direction and on the negative side in the y-axis direction, and forms part of the through-hole 1a. In addition to the flow path 11, the bipolar plate 10 has flow paths including the flow path 12 shown in FIG. 2 formed at each of the four corners of the rectangular shape. These flow paths form part of the through-holes 1b, 1c, and 1d of the water electrolysis cells 1.

[0022] The anode side spacer 20 is a resin frame-shaped member having an opening formed on the inside, and is disposed on the positive side in the z-axis direction of the bipolar plate 10. The opening formed in the anode side spacer 20 allows water flowing through the flow path 11 to flow from the corner where the through hole 1a of the water electrolysis cell 1 is formed to the through hole 1d of the water electrolysis cell 1 formed diagonally to the corner. The structure of the anode side spacer 20 will be described in detail later.

[0023] The membrane electrode assembly 30 is a substantially rectangular plate-like member, and includes a resin frame 31 and a membrane electrode assembly (hereinafter referred to as "MEA") 32. The frame 31 has a rectangular outer shape, and an opening is formed inside in which the MEA 32 is disposed. The MEA 32 includes an electrolyte membrane 33, an anode electrode 34, and a cathode electrode 35.

[0024] The electrolyte membrane 33 is made of, for example, a polyperfluorocarbon sulfonic acid membrane, and is permeable to hydrogen ions and water. An anode 34 and a cathode 35 are joined to both sides of the electrolyte membrane 33, respectively.

[0025] The anode 34 is connected to the negative side of the electrolyte membrane 33 in the z-axis direction. 2The anode electrode 34 has an anode catalyst layer 34a containing arsenic (Ar) and an anode diffusion layer 34b which is a mesh made of titanium (Ti). The anode electrode 34 electrolyzes water using power supplied by a DC power supply 102 to generate oxygen gas and hydrogen ions. Some of the hydrogen ions and water generated at the anode electrode 34 pass through the electrolyte membrane 33 and move to the cathode electrode 35 which is joined to the positive side of the electrolyte membrane 33 in the z-axis direction.

[0026] The cathode electrode 35 has a cathode catalyst layer 35a containing platinum (Pt) and a cathode diffusion layer 35b made of carbon paper. The cathode electrode 35 uses power supplied by a DC power source 102 to convert the hydrogen ions that have passed through the electrolyte membrane 33 into hydrogen gas.

[0027] The cathode side spacer 40 is a plate-like resin member having an opening formed on the inside, and is disposed on the positive side in the z-axis direction of the membrane electrode joint 30. In this embodiment, the cathode side spacer 40 uses a member having the same configuration as the anode side spacer 20, and more specifically, the cathode side spacer 40 is disposed in the state of the anode side spacer 20, but is turned upside down so that the positive and negative sides in the z-axis direction are interchanged.

[0028] 5 is a perspective view of the anode side spacer 20. The anode side spacer 20 includes a frame portion 21, two manifold portions 22 and 23, and a current collector plate 24 for water electrolysis.

[0029] The frame 21 has a rectangular outer shape, and an opening in which a current collector plate 24 for water electrolysis is disposed is formed inside. In the opening of the frame 21, an annular groove 21a is formed on the surface on the positive side in the z-axis direction of the anode side spacer 20 so as to surround the opening. In the frame 21, a flow path 21b which is a part of the through hole 1b and a flow path 21c which is a part of the through hole 1c are formed. Around the opening of the flow path 21b, an annular groove 21d is formed so as to surround the opening of the flow path 21b. Around the opening of the flow path 21b, an annular groove 21e is formed so as to surround the opening of the flow path 21b. Each of the annular grooves 21a, 21d, and 21e formed in the frame 21 suppresses leakage of fluid between the anode side spacer 20 and the gasket by deforming and entering the surface of a gasket disposed between the anode side spacer 20 and the membrane electrode joint 30.

[0030] The manifold portion 22 is a substantially triangular member whose thickness is smaller than that of the frame portion 21. The manifold section 22 is disposed inside the frame section 21 at a corner on the negative side of the x-axis and on the negative side of the y-axis. The manifold section 22 is disposed in the thickness direction of the frame section 21, i.e., in the z-axis direction, on the negative side of the frame section 21 in the z-axis direction (see FIG. 2). The manifold section 22 is formed with a flow path 22a communicating with the flow path 11. The fluid flowing through the flow path 22a passes through the manifold section 22 and flows into the current collector plate 24 for water electrolysis.

[0031] The manifold section 23 is a substantially triangular member whose thickness is thinner than that of the frame section 21, and is disposed inside the frame section 21 on the positive side of the x-axis and the positive side of the y-axis. The manifold section 23 is disposed in the thickness direction of the frame section 21, i.e., in the z-axis direction, on the negative side of the frame section 21 in the z-axis direction. The manifold section 23 has flow paths 23a through which the fluid that has flowed through the water electrolysis current collector plates 24 flows. The fluid flowing out from the water electrolysis current collector plates 24 passes through the manifold section 23 and flows into the flow paths 23a.

[0032] 6 is a perspective view of the current collector plate 24 for water electrolysis. The current collector plate 24 for water electrolysis is formed separately from the bipolar plate 10, the frame portion 21 of the anode side spacer 20, and the manifold portions 22 and 23. The current collector plate 24 for water electrolysis is disposed between the bipolar plate 10 and the anode side diffusion layer 34b. The current collector plate 24 for water electrolysis is a plate-shaped member made of titanium (Ti) coated with platinum (Pt) and has electrical conductivity.

[0033] The water electrolysis current collector 24 is formed by bending a plate-shaped member having a thickness of 0.2 mm or less by cold working, such as embossing or roll pressing. As shown in FIG. 6, the water electrolysis current collector 24 of this embodiment has a plurality of protrusions 25a formed on one main surface 25 and a plurality of recesses 26a formed on the other main surface 26. In this embodiment, the protrusions 25a are formed so that the cross section perpendicular to the x-axis is curved. The recesses 26a are formed on the opposite side of the portion of the one main surface 25 where the protrusions 25a are formed. In the water electrolysis current collector 24 attached to the water electrolysis cell 1, the protrusions 25a are extended along the x-axis direction on the one main surface 25, and are arranged in a row in the y-axis direction. In the water electrolysis current collector 24 of this embodiment, the distance L1 between the tips of two adjacent protrusions 25a is 1 mm or less, and the height H24 of the protrusions 25a in the z-axis direction is 0.6 mm or less.

[0034] As described above, the cathode spacer 40 of the water electrolysis cell 1 has the same configuration as the anode spacer 20, and includes a frame 41, two manifolds 42 and 43, and a flow path structure 44 having a configuration similar to that of the water electrolysis current collector 24. A flow path 42a that is a part of the through hole 1b is formed in the manifold 42 (see FIG. 1). A flow path 43a that is a part of the through hole 1c is formed in the manifold 43 (see FIG. 1).

[0035] FIG. 7 is a diagram illustrating the operation of the water electrolysis cell 1. Water supplied to the water electrolysis cell 1 flows from the flow paths 11 and the flow paths 22a of the anode-side spacer 20 through the manifold portion 22 into the current collector plate 24 for water electrolysis. The water flowing into the current collector plate 24 for water electrolysis flows through one of the main surfaces 25 (between one of the main surfaces 25 and the anode-side catalyst layer 34a) and the other of the main surfaces 26 (between the other of the main surfaces 26 and the bipolar plate 10). The water flowing through one of the main surfaces 25 passes through the anode-side diffusion layer 34b and is electrolyzed in the anode-side catalyst layer 34a. Electricity for electrolyzing water in the anode-side catalyst layer 34a is supplied from the bipolar plate 10 by the current collector plate 24 for water electrolysis and the anode-side diffusion layer 34b, which are electrically connected to the anode-side catalyst layer 34a. Oxygen gas G1 produced by electrolysis of water in the anode catalyst layer 34a passes through one main surface 25 of the water electrolysis current collector 24 together with unreacted water, and is sent to the outside of the water electrolysis cell 1. Hydrogen ions produced by electrolysis of water in the anode catalyst layer 34a pass through the electrolyte membrane 33 together with unreacted water, and reach the cathode electrode 35. The hydrogen ions that have reached the cathode electrode 35 are transported to the cathode catalyst layer 35a. The hydrogen gas G2 is then sent to the outside of the water electrolysis cell 1 through the cathode diffusion layer 35b and the flow path structure 44.

[0036] Fig. 8 is a diagram illustrating the function of the water electrolysis current collector 24. Fig. 8 shows cross sections perpendicular to the x-axis of the water electrolysis current collector 24, the anode-side bipolar plates 10 disposed on both sides of the water electrolysis current collector 24, and the anode-side diffusion layer 34b when the water electrolysis cell 1 is electrolyzing water.

[0037] The current collector plate 24 for water electrolysis is configured such that water flows on both the one main surface 25 side and the other main surface 26 side. Specifically, as shown in FIG. 8, the surface 22b of the manifold portion 22 of the anode side spacer 20 is located approximately midway between the bipolar plate 10 and the anode side diffusion layer 34b, and the water flowing along the surface 22b flows into both the one main surface 25 side and the other main surface 26 side. As a result, at each of the cross-sectional positions Cs1, Cs2, and Cs3 in FIG. 8, the water flows on either the one main surface 25 side or the other main surface 26 side depending on the shape of the current collector plate 24 for water electrolysis. Specifically, at the cross-sectional position Cs1, the current collector plate 24 for water electrolysis is located near the bipolar plate 10, so that the water flows between the one main surface 25 and the anode side diffusion layer 34b (reference symbol Sv1 in FIG. 8). At cross-sectional position Cs3, the water electrolysis current collector 24 is located near the anode-side diffusion layer 34b, so that the water flows between the other main surface 26 and the bipolar plate 10 (Sv3 in FIG. 8). At cross-sectional position Cs2, the water electrolysis current collector 24 is located approximately halfway between the bipolar plate 10 and the anode-side diffusion layer 34b, so that half of the water flows between one main surface 25 and the anode-side diffusion layer 34b, and the other half flows between the other main surface 26 and the bipolar plate 10 (Sv2 in FIG. 8).

[0038] As described above, part of the water flowing between the one principal surface 25 and the anode side diffusion layer 34b permeates into the anode side diffusion layer 34b and is electrolyzed in the anode side catalyst layer 34a to generate oxygen gas G1. As a result, the flow rate of the water flowing between the one principal surface 25 and the anode side diffusion layer 34b decreases, and the amount of oxygen gas G1 contained in the water increases from the upstream to the downstream of the flow path in the water electrolysis cell 1. Therefore, the amount of water per unit volume between the one principal surface 25 and the anode side diffusion layer 34b decreases from the upstream to the downstream of the flow path.

[0039] The water flowing between the other principal surface 26 and the bipolar plate 10 continues to flow as is, and the flow rate of the water does not change from the upstream to downstream of the flow path in the water electrolysis cell 1. Furthermore, since oxygen gas G1 does not get mixed in, as occurs on the side of one principal surface 25, the amount of water per unit volume between the other principal surface 26 and the bipolar plate 10 does not change either.

[0040] In the current collector plate 24 for water electrolysis, the tips 25b of the protrusions 25a formed on one main surface 25 are in contact with the anode-side diffusion layer 34b, and the other main surface 26 is in contact with the bipolar plate 10. As a result, a current flows from the bipolar plate 10 to the anode-side catalyst layer 34a through the current collector plate 24 for water electrolysis and the anode-side diffusion layer 34b. The contact portion Cp1 between the tips 25b of the protrusions 25a and the anode-side diffusion layer 34b is a place where current is likely to concentrate, and is therefore likely to generate heat and increase in temperature. In the current collector plate 24 for water electrolysis of this embodiment, water flows between the other main surface 26 and the bipolar plate 10 in the immediate vicinity of the contact portion Cp1, and the contact portion Cp1 is cooled by this water. As a result, it is possible to suppress a temperature increase at the contact portion Cp1.

[0041] FIG. 9 is a diagram illustrating the operation of a water electrolysis cell of a first comparative example. The water electrolysis cell 9 of the first comparative example shown in FIG. 9 is different from the present embodiment in the shape of the bipolar plates 10. Specifically, in the water electrolysis cell 9, each of the two bipolar plates 10 has an annular 9, the bipolar plate 10 is provided with a plurality of contact parts 16 that are in contact with either the anode-side diffusion layer 34b or the cathode-side diffusion layer 35b. The contact parts 16 are provided on the anode-side diffusion layer 34b side of the bipolar plate 10 or on the cathode-side diffusion layer 35b, and protrude from the bipolar plate 10. This allows water that permeates the anode-side diffusion layer 34b to flow between the adjacent contact parts 16.

[0042] In the water electrolysis cell 9 of the first comparative example, a current flows from the bipolar plate 10 to the anode catalyst layer 34a through the contact parts 16 and the anode diffusion layer 34b. Therefore, the contact parts Cp0 between the contact parts 16 and the anode diffusion layer 34b are likely to be a location where the current is likely to concentrate, and are therefore likely to generate heat and increase in temperature. Furthermore, as described in the explanation of FIG. 8, in the water electrolysis cell 9, the amount of oxygen gas G1 contained in the water increases from the upstream to the downstream of the flow path, and the amount of water per unit volume decreases from the upstream to the downstream of the flow path. This results in insufficient cooling of the contact parts Cp0, and a heat spot occurs. If a heat spot occurs, the water electrolysis cell 6 may be damaged, so it is necessary to reduce the power output by the DC power supply 102, and the amount of hydrogen gas generated by the water electrolysis cell 9 decreases.

[0043] FIG. 10 is a schematic diagram of a water electrolysis system 200 of a second comparative example. The water electrolysis system 200 is different from the water electrolysis system 100 of the present embodiment in that it includes a cooling system 202 for cooling a water electrolysis apparatus 201 including the water electrolysis cell 9 of the first comparative example. In the cooling system 202, as shown in FIG. 10, for example, the pure water stored in the pure water storage tank 107 is supplied to the water storage tank 202b using a supply pump 202a. A part of the pure water stored in the water storage tank 202b is cooled in a heat exchanger 202c and then supplied to the anode side of the water electrolysis apparatus 201. A part of the pure water stored in the water storage tank 202b is pressurized by a circulation pump 202d, impurities are removed using a water purifier 202e, and then the part is supplied to the cathode side of the water electrolysis apparatus 201. In this way, the contact portion Cp0 is cooled by supplying cooling water to each of the two bipolar plates 10 included in the water electrolysis apparatus 2011. However, in order to suppress corrosion of components, the cooling water supplied by the cooling system 202 is desirably pure water of the same level as the water used for electrolysis, and requires water quality management, such as measuring electrical conductivity, an ion exchange system, etc. For this reason, the water electrolysis system 200 is larger than the water electrolysis system 100 of the present embodiment.

[0044] Next, two evaluation tests for the water electrolysis cell 1 of this embodiment will be described. In the first evaluation test, the degree of contact between the protrusions 25a of the water electrolysis current collector 24 incorporated in the water electrolysis cell 1 and the anode diffusion layer 34b was confirmed.

[0045] Fig. 11 shows the results of the first evaluation test. Fig. 11 shows the results of measuring the surface pressure of the protruding portion 25a of the current collector 24 for water electrolysis, using pressure-sensitive paper, when the water electrolysis cell 1 was assembled using the current collector 24 for water electrolysis prepared by embossing. As shown in Fig. 11, it was confirmed that the load of the protruding portion 25a was applied to the entire anode-side diffusion layer 34b. The test results revealed that the load was applied uniformly over the entire water electrolysis cell 1, and that the structure was capable of absorbing distortion and strain at the tolerance level and dimensional error in the z-axis direction that exist in each of the multiple components that make up the water electrolysis cell 1.

[0046] The reason why the results shown in FIG. 11 were obtained in the first evaluation test is because the current collector plate 24 for water electrolysis is produced by cold processing such as embossing and roll pressing. When producing a current collector plate for water electrolysis by cutting, which is a comparative example of a method for producing the current collector plate 24 for water electrolysis, there is a limit to how thin the current collector plate can be made, and it is difficult to deform the current collector plate to absorb the above-mentioned strain. In addition, when deep-drilling is performed in the thickness direction of a plate-shaped member to absorb the above-mentioned strain in the thickness direction with a surface pressing method, which is another comparative example, the size is not changed and the thickness of the current collector plate is not changed. To press the parts, it is necessary to partially stretch the parts. This requires hot pressing by heating, which makes the processing time very long and reduces production efficiency. Furthermore, if one tries to improve production efficiency, the distortion in the direction along the main surface increases, and the deeper the excavation, the greater the deviation, which makes it easy for individual differences in the magnitude of the deviation in the direction along the main surface to occur. For this reason, if the parts are stacked to form a water electrolysis cell, there is a risk that they will not be able to be sealed.

[0047] In this embodiment, the current collector plate 24 for water electrolysis is produced by cold working such as embossing or roll pressing as described above, and therefore the convex portions 25a and the concave portions 26a are formed by folding the plate-shaped member rather than stretching it. As a result, the size of the plate-shaped member is reduced, but the amount of reduction can be easily predicted from the sizes of the convex portions 25a and the concave portions 26a, and therefore sealing can be ensured by separately preparing the frame portion 21 and the manifold portions 22 and 23 in accordance with this amount of reduction.

[0048] In the second evaluation test, the cell voltage of the water electrolysis cell was evaluated. Specifically, the cell voltage relative to the power input to the water electrolysis cell was measured, and the efficiency (cell efficiency) calculated using the measured cell voltage was compared with that of a comparative example. In the second evaluation test, the output voltage of the water electrolysis cell 1 including the water electrolysis current collector 24 of this embodiment was compared with the output voltage of a water electrolysis cell including a water electrolysis current collector produced by cutting as a comparative example.

[0049] 12 is a diagram showing the results of the second evaluation test. In the second evaluation test, the water electrolysis cell was charged at a current of 3 A / cm 2 power measured against 1cm 2 The cell efficiency is calculated from the cell voltage per 100 kV. In this evaluation test, the measurement temperature was 80° C. As shown in FIG. 12, it was revealed that the water electrolysis cell 1 of this embodiment exhibits a higher cell efficiency than the water electrolysis cell of the comparative example. This shows that the water electrolysis cell 1 of this embodiment exhibits a higher cell efficiency than the water electrolysis cell of the comparative example. 2 Even when operated at such a relatively high current density, the cell efficiency was higher than that of the water electrolysis cell of the comparative example, making it clear that this is a high-performance water electrolysis cell.

[0050] In the water electrolysis cell of the comparative example, water is consumed by electrolysis on the anode side and moves to the cathode side together with hydrogen ions, so that the flow rate of water decreases from the upstream to the downstream of the flow path. Furthermore, oxygen gas is generated on the anode side and is contained as bubbles in the water flowing between the bipolar plate and the anode side diffusion layer. For example, when 18 grams of water is electrolyzed, 11.2 liters of oxygen gas is generated, so the proportion of bubbles contained in the water flowing between the bipolar plate and the anode side diffusion layer increases rapidly. Therefore, on the downstream side of the flow path, water flows in the oxygen gas in the form of particles, so there is a risk of insufficient water supply to the diffusion layer. Furthermore, oxygen gas has a lower thermal conductivity than water, so that the anode side diffusion layer is difficult to cool by the fluid flowing between the bipolar plate and the diffusion layer. Meanwhile, in the current path from the bipolar plate to the anode-side diffusion layer via the current collector for water electrolysis, electrical resistance tends to be high at locations where current is concentrated, such as the contact portion between the current collector for water electrolysis and the diffusion layer, which may result in the formation of heat spots and localized deterioration of components.

[0051] In the water electrolysis cell 1 of the present embodiment described above, the tip 25b of the protrusion 25a formed on one main surface 25 of the plate-shaped water electrolysis current collector 24 is in contact with the anode-side diffusion layer 34b, and a current flows from the bipolar plate 10 to the anode-side catalyst layer 34a via the water electrolysis current collector 24 and the anode-side diffusion layer 34b. As a result, current is concentrated at the contact portion Cp1 between the tip 25b of the protrusion 25a and the anode-side diffusion layer 34b, which is likely to increase in temperature. In the water electrolysis cell 1, the water electrolysis current collector 24 has a recess 26a through which water can flow formed on the other main surface 26 opposite to the portion on the one main surface 25 where the protrusion 25a is formed. As a result, the tip 25b of the protrusion 25a is in contact with the anode-side diffusion layer 34b via the water electrolysis current collector 24. The contact portion Cp1 between the tip 25b of the protrusion 25a and the anode diffusion layer 34b can be efficiently cooled. Furthermore, the water electrolysis current collector 24 is formed to restrict the movement of gas flowing on the one main surface 25 side to the inside of the recess 26a. Since oxygen gas G1 is generated by electrolysis of water on the one main surface 25 side, the amount of oxygen gas G1 contained in the water flowing on the one main surface 25 side increases as it moves downstream, and the cooling efficiency decreases. On the other hand, since the water flowing on the other main surface 26 side does not contain oxygen gas G1 even downstream, the cooling efficiency is maintained and the contact portion Cp1 between the tip 25b of the protrusion 25a and the anode diffusion layer 34b can be cooled. Therefore, the occurrence of heat spots in the water electrolysis cell 1 can be suppressed, and deterioration of the members can be suppressed, and the electrolysis of water can be stably performed.

[0052] Furthermore, the water electrolysis cell 1 of this embodiment intensively cools the contact area Cp1 between the water electrolysis current collector 24 and the anode side diffusion layer 34b, which is likely to generate heat due to current concentration when a current flows from the bipolar plate 10 to the anode side catalyst layer 34a. As a result, while a water electrolysis cell 9 as shown in Fig. 9, which does not have a cooling mechanism, is limited to operation at a low current density because the temperature rises when the current density is increased, the water electrolysis cell 1 of this embodiment can be operated at a high current density. As a result, more hydrogen gas can be produced.

[0053] When flow paths are formed in bipolar plates as in the water electrolysis cell 9 of the comparative example shown in FIG. 9, the intervals between the flow paths need to be increased to form relatively deep flow paths, resulting in a reduced amount of water supply. Furthermore, if a defect such as corrosion occurs in the flow paths, the entire bipolar plate needs to be replaced. In the water electrolysis cell 1 of this embodiment, the current collector 24 for water electrolysis is formed separately from the bipolar plate 10, the frame 21 of the anode side spacer 20, and the manifolds 22 and 23. As a result, the current collector 24 for water electrolysis together with the bipolar plate 10 and the anode side diffusion layer 34b can form relatively deep flow paths through which water flows, and if a defect occurs in the flow paths, the defect can be addressed by replacing only the current collector 24 for water electrolysis.

[0054] Furthermore, in the water electrolysis cell 1 of this embodiment, water supplied from the flow paths 11 and the flow paths 22a to the manifold 22 is divided into one main surface 25 side and the other main surface 26 side of the current collector plate 24 for water electrolysis. As a result, oxygen gas is produced by electrolysis of water on the one main surface 25 side, while water for cooling the contact portion Cp1 between the current collector plate 24 for water electrolysis and the anode-side diffusion layer 34b can be circulated on the other main surface 26 side. As a result, unlike the water electrolysis system 200 of the comparative example shown in Fig. 10, there is no need to provide a new separate mechanism for cooling, and therefore it is possible to prevent the water electrolysis system from becoming large.

[0055] According to the water electrolysis cell 1 of this embodiment, the contact parts Cp1, the temperature of which is likely to increase due to contact between the tips 25b of the protrusions 25a and the anode-side diffusion layer 34b, are distributed relatively evenly on the contact surface between the water electrolysis current collector 24 and the anode-side diffusion layer 34b, so that local temperature increases can be suppressed. Furthermore, the recesses 26a, through which water flows to efficiently cool the contact parts Cp1 between the tips 25b of the protrusions 25a and the anode-side diffusion layer 34b, are also formed on the opposite side of the main surface 25 to the part where the protrusions 25a are formed, so that the recesses 26a are relatively evenly distributed on the contact surface between the water electrolysis current collector 24 and the anode-side diffusion layer 34b, so that the contact parts Cp1 between the tips 25b of the protrusions 25a and the anode-side diffusion layer 34b can be cooled. This suppresses local temperature increases, so that water electrolysis can be stably performed.

[0056] Furthermore, in the water electrolysis cell 1 of this embodiment, the distance L1 between the tips 25b of two adjacent protrusions 25a is relatively small, so the flow of water on one main surface 25 is likely to become turbulent. The same applies to the recesses 26a formed on the opposite side of the protrusions 25a. As a result, the flow of water on the one main surface 25 side of the water electrolysis current collector 24 is disturbed, so that even if oxygen gas G1 is contained in the water as the electrolysis of water progresses, the water can be easily supplied to the anode-side diffusion layer 34b. Furthermore, the flow of water on the other main surface 26 side of the water electrolysis current collector 24 is disturbed, so that the cooling effect of the water can be improved. Furthermore, the height H24 of the protrusions 25a has a scale equivalent to the distance L1 between the tips 25b of the two adjacent protrusions 25a, and is relatively deep as a flow path through which water flows. As a result, the pressure loss can be reduced on both the one main surface 25 side and the other main surface 26 side, so that the energy required to flow water can be reduced. Therefore, the energy required for electrolyzing water in the water electrolysis cell 1 can be reduced while the occurrence of heat spots can be suppressed, so that the electrolysis of water can be stably performed.

[0057] In addition, according to the water electrolysis cell 1 of this embodiment, the thickness of the current collector 24 for water electrolysis is relatively small, and therefore the heat capacity is small. As a result, the temperature rise at the start of the water electrolysis cell 1 can be achieved in a relatively short time, and water electrolysis can be performed early and stably. Even if the temperature rises due to current concentration at the contact portion Cp1 between the tip 25b of the protrusion 25a of the current collector 24 for water electrolysis and the anode side diffusion layer 34b, the contact portion Cp1 can be easily cooled by water flowing through the recess 26a due to its small heat capacity. As a result, the temperatures of the current collector 24 for water electrolysis and the anode side diffusion layer 34b can be quickly lowered, and the occurrence of heat spots can be suppressed. As a result, water electrolysis can be performed stably.

[0058] According to the method for producing the water electrolysis cell 1 of the present embodiment, the current collector plate 24 for water electrolysis is formed by cold bending a plate-shaped member having a thickness of 0.2 mm or less without applying heat. This eliminates the need for a heating step, allowing processing in a relatively short time and eliminating the need for heating equipment. In addition, the manufacturing method using bending by cold processing does not generate unnecessary material during processing, allowing more effective use of materials than cutting. Furthermore, in the current collector plate 24 for water electrolysis processed in this manner, the contact portion Cp1 between the tip 25b of the protrusion 25a and the anode-side diffusion layer 34b can be efficiently cooled by water flowing inside the recess 26a, thereby suppressing the occurrence of heat spots. Therefore, the water electrolysis cell 1 capable of stably performing water electrolysis can be produced.

[0059] When a flow path of a bipolar plate is formed as in the water electrolysis cell 9 of the comparative example shown in FIG. 9, it is difficult to form a deep flow path as described above, and the processing time is long. For example, superplastic processing is known as a method for forming deep grooves in a plate-like member made of titanium, but the process takes too much time, making it unrealistic in terms of production. In addition, titanium materials with high purity are not suitable for superplastic processing of titanium, and additives may be added. However, when a titanium member containing such additives is used as a current collector plate for water electrolysis of a water electrolysis cell, the additives may be dissolved and the performance of the water electrolysis cell may be reduced. In addition, the size of the plate changes during processing in superplastic processing, so the sealing position may be shifted. According to the manufacturing method of the water electrolysis cell 1 of this embodiment, the current collector plate 24 for water electrolysis is formed by cold processing in which a plate-like member with a thickness of 0.2 mm or less is bent without applying heat. As a result, it is possible to form a shape with a relatively deep groove, and since the change in size during processing can be predicted, the water electrolysis cell 1 can be manufactured by predicting the displacement of the sealing position. Therefore, it is possible to manufacture a water electrolysis cell 1 capable of stably electrolyzing water.

[0060] <Second embodiment> 13 is a schematic diagram of a current collector for water electrolysis according to the second embodiment. A water electrolysis cell 2 according to the second embodiment differs from the water electrolysis cell 1 according to the first embodiment in the shape of the current collector for water electrolysis.

[0061] The water electrolysis current collector 54 of the water electrolysis cell 2 of this embodiment is a bipolar plate 10 or The anode-side spacer 20 is formed separately from the frame 21 and the manifolds 22 and 23, and is disposed between the bipolar plate 10 and the anode-side diffusion layer 34b. As shown in FIG. 13, the water electrolysis current collector 54 has a protrusion 55a on one main surface 55, the protrusion 55a having a trapezoidal cross section perpendicular to the x-axis. A planar tip 55b of the protrusion 55a is in contact with the anode-side diffusion layer 34b (contact portion Cp2). The other main surface 56 has a recess 56a on the opposite side to the portion on the one main surface 55 where the protrusion 55a is formed. In the water electrolysis current collector 54 attached to the water electrolysis cell 2 of this embodiment, the protrusions 55a are extended along the x-axis direction on the one main surface 55, and a plurality of protrusions 55a are arranged side by side in the y-axis direction. In the current collector plate 54 for water electrolysis, the distance L2 between the tips of two adjacent protrusions 55a is 1 mm or less, and the height H54 in the z-axis direction of the protrusions 55a is 0.6 mm or less. The current collector plate 54 for water electrolysis is formed by bending a plate-shaped member having a thickness of 0.2 mm or less by cold working.

[0062] As described above, according to the water electrolysis cell 2 of this embodiment, the water electrolysis current collector 54 has the recess 56a, through which water can flow, formed on the other main surface 56 opposite to the portion where the protrusion 55a is formed on one main surface 55. This allows the water flowing inside the recess 56a to efficiently cool the contact portion Cp2 between the tip 55b of the protrusion 55a and the anode-side diffusion layer 34b. This prevents the occurrence of heat spots in the water electrolysis cell 2, thereby preventing deterioration of the components and enabling stable water electrolysis.

[0063] Furthermore, in the water electrolysis cell 2 of this embodiment, the convex portion 55a of one main surface 55 is in contact with the anode side diffusion layer 34b at the planar portion. This allows the area of ​​the contact portion Cp2 between the tip 55b of the convex portion 55a and the anode side diffusion layer 34b to be relatively large, thereby ensuring contact between the water electrolysis current collector 54 and the anode side diffusion layer 34b. This reduces the electrical resistance between the water electrolysis current collector 54 and the anode side diffusion layer 34b, thereby suppressing the occurrence of heat spots and enabling stable water electrolysis.

[0064] <Third embodiment> 14 is a schematic diagram of a current collector for water electrolysis according to the third embodiment. The water electrolysis cell 3 according to the third embodiment differs from the water electrolysis cell 1 according to the first embodiment in the shape of the current collector for water electrolysis.

[0065] The water electrolysis current collector 64 included in the water electrolysis cell 3 of this embodiment is formed separately from the bipolar plate 10, the frame 21 of the anode spacer 20, and the manifolds 22 and 23, and is disposed between the bipolar plate 10 and the anode diffusion layer 34b. As shown in FIG. 14, the water electrolysis current collector 64 has a protrusion 65a formed on one main surface 65. The protrusion 65a has a cross-sectional shape perpendicular to the x-axis, which is a so-called step shape in which the size in the y-axis direction changes stepwise. A planar tip 65b of the protrusion 65a is in contact with the anode diffusion layer 34b (contact portion Cp3). A recess 66a is formed on the other main surface 66 on the opposite side to the portion where the protrusion 65a is formed on the one main surface 65. In the water electrolysis current collector 64 attached to the water electrolysis cell 3 of this embodiment, the protrusion 65a is extended along the x-axis direction on the one main surface 65, and a plurality of protrusions 65a are arranged side by side in the y-axis direction. In the current collector plate 64 for water electrolysis, a distance L3 between tips of two adjacent protrusions 65a is 1 mm or less, and a height H64 in the z-axis direction of the protrusions 65a is 0.6 mm or less. The current collector plate 64 for water electrolysis is formed by bending a plate-shaped member having a thickness of 0.2 mm or less by cold working.

[0066] As described above, in the water electrolysis cell 3 of this embodiment, the water electrolysis current collector 64 has a recess 66a through which water can flow formed on the other main surface 66 opposite to the portion where the protrusion 65a is formed on one main surface 65. As a result, the water flowing inside the recess 66a efficiently cools the contact portion Cp3 between the tip 65b of the protrusion 65a and the anode-side diffusion layer 34b. Therefore, in the water electrolysis cell 3, the occurrence of heat spots can be suppressed, and deterioration of the components can be suppressed, enabling stable electrolysis of water.

[0067] Furthermore, in the water electrolysis cell 3 of this embodiment, the protrusions 65a of one main surface 65 are in contact with the anode diffusion layer 34b at their planar portions. This allows the area of ​​the contact portions Cp3 between the tips 65b of the protrusions 65a and the anode diffusion layer 34b to be relatively large, ensuring contact between the water electrolysis current collector 64 and the anode diffusion layer 34b. This reduces the electrical resistance between the water electrolysis current collector 64 and the anode diffusion layer 34b, thereby preventing the occurrence of heat spots and ensuring stable water electrolysis.

[0068] Furthermore, in the water electrolysis cell 3 of this embodiment, the protrusion 65a has a cross-sectional shape perpendicular to the x-axis, which has a so-called stepped shape in which the size in the y-axis direction changes stepwise. This allows the protrusion 65a to expand and contract to some extent in the z-axis direction, thereby absorbing distortion and strain at the tolerance level present in each of the multiple components that constitute the water electrolysis cell 3.

[0069] <Fourth embodiment> 15 is a schematic diagram of a current collector for water electrolysis according to the fourth embodiment. A water electrolysis cell 4 according to the fourth embodiment differs from the water electrolysis cell 1 according to the first embodiment in the shape of the current collector for water electrolysis.

[0070] The water electrolysis current collector 74 included in the water electrolysis cell 4 of this embodiment is formed separately from the bipolar plate 10, the frame 21 of the anode spacer 20, and the manifolds 22 and 23, and is disposed between the bipolar plate 10 and the anode diffusion layer 34b. As shown in FIG. 15, the water electrolysis current collector 74 has a protrusion 75a formed on one main surface 75. As shown in FIG. 15, the protrusion 75a has a cross-sectional shape perpendicular to the x-axis in which a semicircular portion protruding in the positive direction of the z-axis and an arc-shaped portion with a central angle of 90 degrees protruding in the negative direction of the z-axis are connected by a straight line 77. A planar tip 75b of the protrusion 75a is in contact with the anode diffusion layer 34b (contact portion Cp4). A recess 76a is formed on the other main surface 76 on the opposite side to the portion where the protrusion 75a is formed on the one main surface 75. In the current collector plate 74 for water electrolysis attached to the water electrolysis cell 4 of this embodiment, the protrusions 75a extend along the x-axis direction on one main surface 75, and are arranged in a row in the y-axis direction. In the current collector plate 74 for water electrolysis, the distance L4 between the tips of two adjacent protrusions 75a is 1 mm or less, and the height H74 of the protrusions 75a in the z-axis direction is 0.6 mm or less. The current collector plate 74 for water electrolysis is formed by bending a plate-shaped member having a thickness of 0.2 mm or less by cold working.

[0071] As described above, according to the water electrolysis cell 4 of this embodiment, the water electrolysis current collector 74 has a recess 76a through which water can flow formed on the other main surface 76 opposite to the portion where the protrusion 75a is formed on one main surface 75. This allows the water flowing inside the recess 76a to efficiently cool the contact portion Cp4 between the tip 75b of the protrusion 75a and the anode-side diffusion layer 34b. This prevents the occurrence of heat spots in the water electrolysis cell 4, thereby preventing deterioration of the components and enabling stable water electrolysis.

[0072] Furthermore, in the water electrolysis cell 4 of this embodiment, the protrusion 75a has a shape in which an arc shape on the positive side of the z axis direction and an arc shape on the negative side of the z axis direction are connected by a straight line. This allows the protrusion 75a to expand and contract to some extent along the z axis direction, thereby absorbing distortion and strain at the tolerance level that exists in each of the multiple components that constitute the water electrolysis cell 4.

[0073] In addition, according to the water electrolysis cell 4 of this embodiment, the protrusion 75a is formed in a circular shape on the positive side in the z-axis direction. The protrusion 75a has an arc shape. Thus, unlike the protrusion 55a of the second embodiment and the protrusion 65a of the third embodiment, the protrusion 75a can contact the anode diffusion layer 34b with its curved surface. This makes it possible to prevent damage to the anode diffusion layer 34b due to contact with the water electrolysis current collector 74.

[0074] <Fifth embodiment> Fig. 16 is a perspective view of a current collector plate for water electrolysis according to a fifth embodiment. Fig. 17 is a cross-sectional view of a current collector plate for water electrolysis according to the fifth embodiment. The water electrolysis cell according to the fifth embodiment differs from the water electrolysis cell 1 according to the first embodiment in the shape of the current collector plate for water electrolysis.

[0075] The water electrolysis current collector 84 included in the water electrolysis cell of this embodiment is formed separately from the bipolar plate 10, the frame 21 of the anode spacer 20, and the manifolds 22 and 23, and is disposed between the bipolar plate 10 and the anode diffusion layer 34b. As shown in FIG. 16, the water electrolysis current collector 84 has a plurality of protrusions 85a formed on one main surface 85. The plurality of protrusions 85a are formed to have a substantially cylindrical shape, and the planar tips of the protrusions 85a are in contact with the anode diffusion layer 34b. Here, the "circle" that is the cross-sectional shape of the "substantially cylindrical shape" is not limited to a perfect circle, and may also include a shape that appears circular or elliptical at first glance. A recess 86a is formed on the other main surface 86 on the opposite side to the portion where the protrusion 85a is formed on the one main surface 85 (see FIG. 17, which is a cross-sectional view taken along line α-α in FIG. 16). 17, a plurality of protrusions 86b having a substantially cylindrical shape are formed on the other main surface 86, and recesses 85b are formed on the other main surface 86 on the opposite side to the portions where the protrusions 86b are formed. The planar tips of the protrusions 86b are in contact with the bipolar plate 10.

[0076] In this embodiment, as shown in Fig. 16, two rows of six convex portions 85a arranged in the y-axis direction and two rows of six concave portions 85b arranged in the y-axis direction are alternately arranged on one main surface 85 of a current collector plate 84 for water electrolysis from the negative side to the positive side of the x-axis. As shown in Fig. 17, one row of six convex portions 85a arranged in the y-axis direction and another row of six convex portions 85a arranged behind the row are alternately arranged, so that, for example, water flowing along one main surface 85 is likely to collide with the convex portions 85a. This configuration is also the same for the other main surface 86. The current collector plate 84 for water electrolysis is formed by bending a plate-shaped member having a thickness of 0.2 mm or less by cold working.

[0077] As described above, in the water electrolysis cell of this embodiment, the water electrolysis current collector 84 has a recess 86a through which water can flow formed on the other main surface 86 opposite to the portion where the protrusion 85a is formed on one main surface 85. This allows the water flowing inside the recess 86a to efficiently cool the contact portion between the tip of the protrusion 85a and the anode-side diffusion layer 34b. This prevents the occurrence of heat spots, suppresses deterioration of components, and ensures stable water electrolysis.

[0078] According to the water electrolysis cell of this embodiment, the multiple protrusions 85a formed on the current collector plate 84 for water electrolysis are formed at a distance from each other, and one protrusion 85a is formed in two different directions. As a result, the water flowing along one main surface 85 of the current collector plate 84 for water electrolysis collides with the protrusions 85a, and the flow direction changes. This is also true for the other main surface 86 on which the protrusions 86b are formed. As a result, the flow of water on one main surface 85 side of the current collector plate 84 for water electrolysis is disturbed, so that even if the water contains oxygen gas G1 as the electrolysis of water progresses, the water can be easily supplied to the anode-side diffusion layer 34b. Furthermore, the flow of water on the other main surface 86 side of the current collector plate 84 for water electrolysis is disturbed, so that the cooling effect of the water can be improved. Therefore, the occurrence of heat spots can be suppressed, and the electrolysis of water can be stably performed.

[0079] Sixth embodiment 18 is a schematic diagram of an anode side spacer according to the sixth embodiment. The water electrolysis cell according to the sixth embodiment differs from the water electrolysis cell 1 according to the first embodiment in the shape of the anode side spacer.

[0080] The water electrolysis cell of the sixth embodiment includes a bipolar plate 10, an anode side spacer 90, a membrane electrode joint 30, a cathode side spacer 40, and a plurality of gaskets (not shown). In the water electrolysis cell of the sixth embodiment, the bipolar plate 10, a gasket, the anode side spacer 90, a gasket, the membrane electrode joint 30, a gasket, the cathode side spacer 40, and a gasket are stacked in this order from the negative side in the z-axis direction.

[0081] The anode side spacer 90 is a resin frame-shaped member having an opening formed on the inside, and includes a frame 21, two manifolds 22, 23, and a current collector plate for water electrolysis 24. In this embodiment, gaps 97, 98 are formed between each of the manifolds 22, 23 and the current collector plate for water electrolysis 24 disposed inside the frame 21.

[0082] FIG. 19 is a diagram illustrating the effect of changing the position of the manifold section. In this embodiment, the surface 22b of the manifold section 22 is disposed at a position shown in FIG. 19(A) with respect to the current collector plate 24 for water electrolysis. Water in the manifold section 22 flows on the positive side in the z-axis direction from the surface 22b. When the surface 22b of the manifold section 22 is at the position Mp in FIG. 19(A), the water flowing through the manifold section 22 flows into the current collector plate 24 for water electrolysis at a flow rate according to the ratio of the area between one main surface 25 of the opening portion Op1 shown in FIG. 19(A) and the anode-side diffusion layer 34b to the area between the other main surface 26 and the bipolar plate 10. In the state of FIG. 19(A), the flow rate of water between one main surface 25 and the anode-side diffusion layer 34b is greater than the flow rate of water between the other main surface 26 and the bipolar plate 10.

[0083] On the other hand, suppose that the surface 22b of the manifold portion 22 is disposed in a position in the negative direction of the z axis as shown in FIG. 19(B) from the position Mp shown in FIG. 19(A) with respect to the current collector plate 24 for water electrolysis (see the outline arrow A6 in FIG. 19(B)). In this case, the area of ​​the opening portion Op2 between the other main surface 26 and the bipolar plate 10 becomes relatively larger than that in the state shown in FIG. 19(A), and therefore the flow rate of water between the other main surface 26 and the bipolar plate 10 becomes greater than the flow rate of water between the one main surface 25 and the anode-side diffusion layer 34b. In this way, the flow rate of water in the recesses 26a is increased, thereby improving the degree of cooling of the current collector plate 24 for water electrolysis and the anode-side diffusion layer 34b.

[0084] As described above, according to the water electrolysis cell of this embodiment, the flow rate of water between one principal surface 25 and the anode side diffusion layer 34b and the flow rate of water between the other principal surface 26 and the bipolar plate 10 can be adjusted by changing the position of the surface 22b of the manifold portion 22 relative to the water electrolysis current collector plate 24. This makes it possible to adjust the degree of cooling in accordance with the output characteristics of the water electrolysis cell, thereby improving the output characteristics of the water electrolysis cell.

[0085] <Modifications of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit and scope of the invention. For example, the following modifications are also possible.

[0086] [Variation 1] In the above embodiment, the distance between the tips of two adjacent protrusions in the current collector plate for water electrolysis is 1 mm or less, and the height in the z-axis direction is 0.6 mm or less. The distance between the tips and the height in the z-axis direction are not limited to these values. In addition, the current collector plate for water electrolysis is formed by subjecting a plate-shaped member having a thickness of 0.2 mm or less to cold working, for example, embossing or rolling. However, the thickness of the member to be the current collector plate for water electrolysis is not limited to this.

[0087] [Variation 2] In the first embodiment, the protrusion 25a is formed so that the cross-sectional shape perpendicular to the x-axis is a curved shape. In the second embodiment, the protrusion 55a is formed so that the cross-sectional shape perpendicular to the x-axis is a trapezoidal shape. In the third embodiment, the protrusion 65a has a cross-sectional shape perpendicular to the x-axis, which is a so-called step shape in which the size in the y-axis direction changes stepwise. In the fourth embodiment, the protrusion 75a has a cross-sectional shape perpendicular to the x-axis, which has a semicircular part arranged to protrude in the positive direction of the z-axis and an arc-shaped part with a central angle of 90 degrees protruding in the negative direction of the z-axis, connected by a straight line 77. However, the cross-sectional shape of the protrusion is not limited to these.

[0088] [Variation 3] In the above embodiment, the anode electrode 34 of the MEA 32 has the anode catalyst layer 34a and the anode diffusion layer 34b. However, the configuration of the MEA is not limited to this. For example, the anode diffusion layer may be included in the anode spacer.

[0089] [Variation 4] In the fifth embodiment, the multiple protrusions 85a formed on one main surface 85 of the current collector plate 84 for water electrolysis have a substantially cylindrical shape. However, the shape of the protrusions 85a is not limited to this. The cross section may be rectangular or triangular, and may be conical instead of cylindrical.

[0090] [Variation 5] In the above embodiment, the cooling of the current collector plate for water electrolysis on the anode side has been described. The same effect can be said about the flow path structure 44 on the cathode side. Specifically, as shown in FIG. 1 showing the configuration of the water electrolysis system 100, water is supplied to the cathode side via a heat exchanger 104, a circulation pump 100a, and a water purifier 105. This water flows on one main surface side and the other main surface side of the flow path structure 44 on the cathode side. The water flowing on one main surface side is mixed with the generated hydrogen gas, and the water flowing on the other main surface side is not mixed with gas such as hydrogen gas. On the cathode side, the cathode electrode 35 and the bipolar plate 10 are electrically connected by the flow path structure 44, and electricity flows from the cathode electrode 35 to the bipolar plate 10. Therefore, although the contact portion between the flow path structure 44 and the cathode electrode 35 is likely to become hot due to current concentration, the contact portion can be cooled by the water flowing on the other main surface side of the flow path structure 44, thereby preventing the occurrence of heat spots. Therefore, deterioration of the components can be prevented, and water electrolysis can be stably performed.

[0091] Although the present aspect has been described above based on the embodiment and modified examples, the above-mentioned embodiment of the aspect is intended to facilitate understanding of the present aspect and does not limit the present aspect. The present aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents are included in the present aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate. [Explanation of symbols]

[0092] 1,2,3,4,5…Water electrolysis cell 10…Bipolar plate 24,54,64,74,84…Current collector plate for water electrolysis 25,55,75,85...One main surface 25a, 55a, 65a, 75a, 85a...Convex 25b, 55b, 65b, 75b... Tip 26,56,66,76,86…other main surface 26, 56a, 66a, 76a, 86a...Concave 34b...anode side diffusion layer 35b...cathode side diffusion layer G1: Oxygen gas G2…Hydrogen gas L1,L2,L3,L4…distance H24, H54, H64, H74…Height

Claims

1. A water electrolysis cell, comprising: a bipolar plate; a diffusion layer for diffusing water; a plate-shaped current collector for water electrolysis, which is formed separately from the bipolar plate and is disposed between the bipolar plate and the diffusion layer, includes a conductive metal material, has convex portions formed on one main surface, and has concave portions formed on the other main surface on the portion opposite to the portion where the convex portions are formed on the one main surface; wherein the current collector for water electrolysis has the tips of the convex portions in contact with the diffusion layer, and is formed such that water can flow inside the concave portions; regulates the gas flowing on the one main surface side from moving inside the concave portions; a water electrolysis cell.

2. The water electrolysis cell according to Claim 1, wherein the convex portions of the current collector for water electrolysis extend along a first direction on the one main surface and are arranged in a plurality side by side in a direction intersecting the first direction. a water electrolysis cell.

3. The water electrolysis cell according to Claim 2, wherein the current collector for water electrolysis has a distance between the tips of two adjacent convex portions of 1 mm or less; and has a height of the convex portions of 0.6 mm or less. a water electrolysis cell.

4. The water electrolysis cell according to Claim 1, wherein a plurality of substantially cylindrical convex portions are formed on the one main surface of the current collector for water electrolysis. a water electrolysis cell.

5. The water electrolysis cell according to any one of Claims 1 to 4, wherein the thickness of the current collector for water electrolysis is 0.2 mm or less. a water electrolysis cell.

6. A method for manufacturing a water electrolysis cell, comprising: a processing step of forming convex portions on one main surface and concave portions on the other main surface of a plate-shaped member containing a conductive metal material by cold working to form a current collector for water electrolysis; an arranging step of arranging the current collector for water electrolysis between the bipolar plate and the diffusion layer such that the tips of the convex portions formed on the current collector for water electrolysis are in contact with the diffusion layer so that water can flow inside the concave portions and the gas flowing on the one main surface side is regulated from moving inside the concave portions. A method for manufacturing a water electrolysis cell.

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