Separator, electrolytic cell, cell stack, and hydrogen production device

Abstract

This separator is used in an electrolytic cell provided with an anion exchange membrane. The separator is provided with a conductive plate and a frame body that supports the outer peripheral edge of the conductive plate. The frame body is composed of a resin material that is an electrically insulating material. The frame body includes: a supply manifold that is a supply port for an electrolytic solution; and a supply slit that connects the supply manifold and the inner peripheral edge of the frame body. The electrical resistance value of the supply slit is between 50Ω and 1000Ω inclusive. The electrical resistance value is obtained by dividing a value, which is obtained by dividing the length of the supply slit by the cross-sectional area of the supply slit, by the conductivity of the electrolytic solution flowing through the supply slit.

Description

Separator, electrolytic cell, cell stack, and hydrogen production device

[0001] The present disclosure relates to a separator, an electrolysis cell, a cell stack, and a hydrogen production device. This application claims priority from Japanese Patent Application No. 2024-056508, filed March 29, 2024. The entire contents of the Japanese application are incorporated herein by reference.

[0002] Patent Document 1 discloses a water electrolysis device that generates hydrogen by electrolyzing an alkaline aqueous solution. The water electrolysis device includes a stack of electrolytic cells, which are electrolysis cells. Each electrochemical cell includes an anode, a cathode, an anion exchange membrane disposed between the anode and the cathode, an anode separator, and a cathode separator. The anode includes an anode catalyst and an anode power supply. The cathode includes a cathode catalyst and a cathode power supply. Each electrochemical cell for water electrolysis is configured by stacking the anode power supply, anode catalyst, an anion exchange membrane, cathode catalyst, and cathode power supply in this order.

[0003] The anode separator and cathode separator have the same structure. The anode separator will be described as a representative example. The anode separator has an anode supply manifold, an anode discharge manifold, and an anode flow path connecting the anode supply manifold and the anode discharge manifold. The anode flow path has a first communication path connected to the anode supply manifold, a second communication path connected to the anode discharge manifold, and an electrode-passing flow path connecting the first communication path and the second communication path. The alkaline aqueous solution is supplied to the anode through the anode supply manifold, the first communication path, and the electrode-passing flow path. The alkaline aqueous solution that has passed through the anode is discharged from the anode discharge manifold through the second communication path. The alkaline aqueous solution is also supplied to the cathode through the cathode supply manifold, the first communication path, and the electrode-passing flow path. The alkaline aqueous solution that has passed through the cathode is discharged from the cathode discharge manifold through the second communication path.

[0004] In an electrochemical cell for water electrolysis, oxygen is generated at the anode and hydrogen is generated at the cathode by applying a voltage between the anode and the cathode while an alkaline aqueous solution is supplied to the anode and the cathode.

[0005] JP 2023-73782 A

[0006] The separator of the present disclosure is used in an electrolysis cell equipped with an anion exchange membrane. The separator includes a conductive plate and a frame supporting the outer peripheral edge of the conductive plate. The frame is made of an electrically insulating resin. The frame has a supply manifold serving as a supply port for the electrolytic solution and a supply slit connecting the supply manifold to the inner peripheral edge of the frame. The supply slit has an electrical resistance value of 50 Ω or more and 1000 Ω or less. The electrical resistance value is the value obtained by dividing the length of the supply slit by the cross-sectional area of ​​the supply slit and then dividing the result by the conductivity of the electrolytic solution flowing through the supply slit.

[0007] Fig. 1 is a plan view showing a separator of an embodiment, Fig. 2 is a side view showing an outline of a hydrogen production device of an embodiment, and Fig. 3 is a partial cross-sectional view of an electrolysis cell provided in the hydrogen production device of an embodiment.

[0008] [Problem to be Solved by the Present Disclosure] When an electrolyte solution such as an alkaline aqueous solution is supplied to each electrolytic cell in parallel from a common supply source, and the anode flow path and cathode flow path are filled with the electrolyte solution, a self-discharge current flows through the electrolyte solution in the anode flow path and the cathode flow path in accordance with the potential difference between each electrolytic cell. This self-discharge current is called a shunt current. When a shunt current flows, the loss rate increases. The larger the shunt current, the larger the loss rate. Furthermore, the larger the number of electrolytic cells, the larger the loss rate. Increasing the number of electrolytic cells to increase the amount of hydrogen produced increases the loss rate.

[0009] An object of the present disclosure is to provide a separator that can reduce the loss rate due to shunt current.

[0010] [Advantages of the Present Disclosure] The separator of the present disclosure can reduce the loss rate due to shunt current.

[0011] <Description of Embodiments of the Present Disclosure> First, embodiments of the present disclosure will be listed and described.

[0012] (1) A separator according to one embodiment of the present disclosure is used in an electrolytic cell equipped with an anion exchange membrane. The separator includes a conductive plate and a frame supporting the outer peripheral edge of the conductive plate. The frame is made of an electrically insulating resin. The frame includes a supply manifold serving as a supply port for the electrolytic solution and a supply slit connecting the supply manifold to the inner peripheral edge of the frame. The supply slit has an electrical resistance value of 50 Ω or more and 1000 Ω or less. The electrical resistance value is the value obtained by dividing the length of the supply slit by the cross-sectional area of ​​the supply slit and then dividing the result by the conductivity of the electrolytic solution flowing through the supply slit.

[0013] In the separator (1) above, the electrical resistance value of the supply slit is 50 Ω or more, which makes it easier to reduce the shunt current compared to when the electrical resistance value of the supply slit is less than 50 Ω. Therefore, the separator (1) above can reduce the loss rate due to the shunt current. Therefore, the separator (1) above can construct a hydrogen production device that can efficiently produce hydrogen. In the separator (1) above, the electrical resistance value of the supply slit is 1000 Ω or less, which makes it possible to reduce flow resistance and pressure loss compared to when the electrical resistance value of the supply slit is more than 1000 Ω.

[0014] (2) In the separator of (1) above, the supply slit may have a bent portion that is folded back.

[0015] The length of the supply slit having a bent portion tends to be long, which tends to increase the electrical resistance of the supply slit. Therefore, the separator (2) mentioned above tends to reduce the loss rate.

[0016] (3) In the separator of (1) or (2), the frame may have an exhaust manifold that is an exhaust port for gas generated by electrolysis of water contained in the electrolytic solution, and an exhaust slit that connects the exhaust manifold and the inner peripheral edge portion. The exhaust slit has a bent portion that is folded back.

[0017] The length of the discharge slit with the bent portion tends to be long. The gas tends to accumulate in the bent portion. The gas has a lower electrical conductivity than the electrolyte. Therefore, the electrical resistance of the discharge slit tends to be high. Therefore, the separator (3) tends to reduce the loss rate.

[0018] (4) An electrolysis cell according to one aspect of the present disclosure includes the separator according to any one of (1) to (3), an anode, an anion exchange membrane, and a cathode.

[0019] The electrolytic cell of (4) above can reduce the loss rate by including the separator.

[0020] (5) A cell stack according to one aspect of the present disclosure includes the electrolysis cell described above in (4).

[0021] The cell stack of (5) above can reduce the loss rate by including the electrolysis cell.

[0022] (6) A hydrogen production device according to one aspect of the present disclosure includes the cell stack described above in (5).

[0023] The hydrogen production device of (6) above, by including the cell stack, can reduce the loss rate. Therefore, the hydrogen production device of (6) above can reduce power consumption when the amount of hydrogen produced is constant. Furthermore, the hydrogen production device of (6) above can increase the amount of hydrogen produced when the amount of power consumed is constant.

[0024] <Details of the Embodiments of the Present Disclosure> Specific examples of the separator, electrolysis cell, cell stack, and hydrogen production device of the present disclosure are described below with reference to the drawings. The same reference numerals in the figures indicate the same items. The shapes, sizes, positional relationships, and the like shown in each figure are depicted for the purpose of clarifying the description and do not necessarily represent the actual shapes, sizes, positional relationships, and the like. The present invention is not limited to the configurations shown in the embodiments, but is defined by the claims, and all modifications within the meaning and scope of the claims are intended to be included.

[0025] <<Embodiment>> [Separator] A separator 3 according to an embodiment will be described with reference to Fig. 1. The separator 3 shown in Fig. 1 is a component constituting a cell stack 2 included in a hydrogen production device 1, which will be described later with reference to Fig. 2. The separator 3 includes a conductive plate 31 and a frame 32 that supports the outer peripheral edge of the conductive plate 31. The frame 32 has a first supply manifold 33 and a first supply slit 34. One of the features of the separator 3 is that the electrical resistance value of the first supply slit 34 satisfies a specific range.

[0026] When the cell stack 2 shown in FIG. 2 is constructed, the separators 3 are disposed on both ends of each electrolysis cell 20. That is, the separators 3 are disposed on both sides of an assembly in which the anode 22, the anion exchange membrane 21, and the cathode 23 are stacked. The separators 3 separate adjacent assemblies. As described below, the cell stack 2 includes a stack 2a in which a plurality of electrolysis cells 20 are stacked, and a first current collector 41 and a second current collector 42 disposed on both sides of the stack 2a in the stacking direction and connected to a power source. When the first current collector 41 is the cathode, the separators 3 are disposed between adjacent assemblies, between the cathode 23 and the first current collector 41 located at one end of the stack 2a in the stacking direction, and between the anode 22 and the second current collector 42 located at the other end of the stack 2a in the stacking direction. One separator 3 is disposed between each of the assemblies. One assembly is provided between adjacent separators 3. At the intermediate position in the stacking direction of the laminate 2a, the anode 22, the anion exchange membrane 21, the cathode 23, and the separator 3 are repeatedly stacked in this order. The separator 3 at the end adjacent to the first current collector plate 41, the separator 3 at the end adjacent to the second current collector plate 42, and the intermediate separator 3 located between these separators 3 at these ends all have the same configuration.

[0027] The conductive plate 31 may be formed of, for example, a first conductive material or a composite material. The conductive plate 31 may be formed of a coated conductive plate. The coated conductive plate includes a substrate and one or more coating layers covering the surface of the substrate. The substrate is formed of a first conductive material. The coating layer is formed of a second conductive material. The composite material includes the first conductive material and a resin. The first conductive material may be a metal or a non-metal. The metal may be, for example, one or more selected from the group consisting of iron alloys, titanium, titanium alloys, copper, copper alloys, nickel, nickel alloys, aluminum, aluminum alloys, and zinc. The iron alloy may be, for example, steel. The steel may be various steels such as stainless steel, silicon chromium steel, or carbon steel. The non-metal may be a carbon material or a conductive ceramic. The carbon material may be, for example, graphite, carbon black, or diamond-like carbon. The second conductive material may be, for example, a material that has better oxidation resistance to an electrolyte than the first conductive material. The second conductive material is, for example, one or more metals selected from the group consisting of platinum group metals, gold, silver, and nickel. The resin in the composite material is, for example, one selected from the group consisting of polyethylene resin, polypropylene resin, polytetrafluoroethylene resin, perfluoroalkoxyalkane resin, perfluoroethylenepropene copolymer, and polyphenylene sulfide resin.

[0028] The inner peripheral edge 32i of the frame 32 has, for example, a step or recess, although not shown. The conductive plate 31 is disposed in this step or recess. The conductive plate 31 and the frame 32 are prepared, and the conductive plate 31 is disposed in the step or recess of the frame 32, thereby forming the separator 3 in which the conductive plate 31 and the frame 32 are combined. The frame 32 may be formed, for example, by injection molding on the outer peripheral edge of the conductive plate 31. The conductive plate 31 is prepared, and the outer peripheral edge of the conductive plate 31 is injection molded to form the separator 3 in which the frame 32 is integrated with the outer peripheral edge of the conductive plate 31.

[0029] The shapes of the outer peripheral edge 32e and inner peripheral edge 32i of the frame 32 correspond to the shape of the outer peripheral edge of the conductive plate 31. In this embodiment, the frame 32 has a rectangular frame shape in a plan view. The frame 32 has a first side 321 and a second side 322 facing each other, and a third side 323 and a fourth side 324 connecting both ends of the first side 321 and the second side 322. The first side 321 is located at the bottom of FIG. 1 and extends in the left-right direction. The second side 322 is located at the top of FIG. 1 and extends in the left-right direction. The third side 323 is located on the left side of FIG. 1 and extends in the up-down direction. The third side 323 connects the left ends of the first side 321 and the second side 322. The fourth side 324 is located on the right side of FIG. 1 and extends in the vertical direction. The fourth side 324 connects the right ends of the first side 321 and the second side 322. In FIG. 1 , the lengths of the first side 321 and the second side 322 along their longitudinal directions, i.e., the lengths along the left and right directions, are shorter than the lengths of the third side 323 and the fourth side 324 along their longitudinal directions, i.e., the lengths along the top and bottom directions. Unlike FIG. 1 , the lengths of the first side 321 and the second side 322 along their longitudinal directions may be longer than the lengths of the third side 323 and the fourth side 324 along their longitudinal directions, or may be equal to the lengths of the third side 323 and the fourth side 324 along their longitudinal directions.

[0030] The frame 32 has an opening that exposes the conductive plate 31. A first recess is formed by the inner circumferential surface of the frame 32 and the first main surface of the conductive plate 31. The first main surface of the conductive plate 31 faces the anode 22. An anode diffusion layer 222 is disposed in the first recess. A second recess is formed by the inner circumferential surface of the frame 32 and the second main surface of the conductive plate 31. The second main surface of the conductive plate 31 is the surface opposite the first main surface and faces the cathode 23. A cathode diffusion layer 232 is disposed in the second recess. To the extent that such a recess can be formed, the size of the outer edge of the conductive plate 31 is made smaller than the size of the outer peripheral edge portion 32e of the frame 32.

[0031] The frame 32 is formed from a resin. The resin forming the frame 32 is an electrically insulating resin. An electrically insulating resin is a resin that has electrical insulation properties against an electrolyte solution. Since the frame 32 is formed from a resin, the outer peripheral surface of the laminate 2a is also formed from a resin. This makes it easier for the laminate 2a to have high electrical insulation against the rod 94 described below. The frame 32 may be formed from a resin that has at least one of alkali resistance and heat resistance in addition to electrical insulation properties. An alkali-resistant resin is a resin that is resistant to an electrolyte solution with a pH of 8 or higher. A heat-resistant resin is a resin that is resistant to temperatures of 80°C or lower. The resin may also be a resin that is resistant to temperatures of 50°C or higher. The resin forming the frame body 32 is, for example, one selected from the group consisting of vinyl chloride resin, polypropylene resin, polyethylene resin, fluororesin, epoxy resin, acrylonitrile butadiene styrene resin, vinylidene chloride resin, polyamide resin, polyester resin, polystyrene resin, acrylic resin, polyvinyl alcohol resin, diacetate resin, triacetate resin, polyphenylsulfone resin, and polycarbonate resin.

[0032] The frame 32 has a first supply manifold 33, a first supply slit 34, a first exhaust manifold 35, a first exhaust slit 36, a second exhaust manifold 37, a second exhaust slit (not shown), and a seal groove (not shown). The first supply manifold 33 and the first supply slit 34 are provided on a first side portion 321. The first exhaust manifold 35, the first exhaust slit 36, and the second exhaust manifold 37 are provided on a second side portion 322.

[0033] The first supply manifold 33 is a supply port for the electrolytic solution to the laminate 2a. The first supply manifold 33 is a through hole that penetrates the first and second main surfaces of the frame 32. The first main surface of the frame 32 is a surface that faces the same direction as the first main surface of the conductive plate 31. The second main surface of the frame 32 is a surface opposite to the first main surface of the frame 32 and faces the same direction as the second main surface of the conductive plate 31. In FIG. 1 , the first main surface is shown. The first supply manifold 33 in this example is provided on the left side of the first side portion 321.

[0034] The first supply slit 34 is a flow path through which the electrolytic solution supplied from the first supply manifold 33 flows. The first supply slit 34 is a flow path that guides the electrolytic solution from the first supply manifold 33 to the inner peripheral edge 32i of the frame 32. The first supply slit 34 is a groove having a bottom surface. The first supply slit 34 is provided on the first main surface of the frame 32 so as to connect the first supply manifold 33 and the inner peripheral edge 32i of the frame 32.

[0035] The electrical resistance of the first supply slit 34 is 50 Ω or more and 1000 Ω or less. The electrical resistance of the first supply slit 34 is the value obtained by dividing the length of the first supply slit 34 by the cross-sectional area of ​​the first supply slit 34 and then dividing the result by the conductivity of the electrolytic solution flowing through the first supply slit 34. When the electrical resistance of the first supply slit 34 is 50 Ω or more, the shunt current is likely to be smaller than when the electrical resistance of the first supply slit 34 is less than 50 Ω. Therefore, the loss rate due to the shunt current is likely to be reduced. When the electrical resistance of the first supply slit 34 is 1000 Ω or less, the flow resistance is smaller than when the electrical resistance of the first supply slit 34 is more than 1000 Ω, and pressure loss can be reduced. Furthermore, because the length of the first supply slit 34 is not too long, the area of ​​the frame 32 is unlikely to increase, and the electrolytic cell 20 is likely to be compact. The electrical resistance value of the first supply slit 34 may be 80Ω or more and 800Ω or less, or 100Ω or more and 500Ω or less.

[0036] The width of the first supply slit 34 is smaller than the minimum length L of the first supply manifold 33. When the first supply slit 34 is viewed in a plane, the width of the first supply slit 34 is the length along a direction perpendicular to the longitudinal direction of the first supply slit 34. The minimum length L is the shortest inner dimension among the inner dimensions passing through the center of the first supply manifold 33. The center of the first supply manifold 33 is the center of the circumscribed circle of the first supply manifold 33. In this example, the minimum length L of the first supply manifold 33 is the length along a direction perpendicular to the longitudinal direction of the first side portion 321. The length of the first supply slit 34 is longer than the shortest distance D between the first supply manifold 33 and the inner peripheral edge portion 32i. Such a first supply slit 34 has a small cross-sectional area and a long length. Therefore, the electrical resistance value is likely to be high and the shunt current is likely to be small. The width of the first supply slit 34 may be, for example, 80% or less, 70% or less, or 50% or less of the minimum length L. The length of the first supply slit 34 may be, for example, 500% or more, 1000% or more, or 2000% or more of the shortest distance D.

[0037] In this example, the first supply slit 34 has a bent portion 341. The bent portion 341 is a portion where the flow direction of the electrolyte changes to the opposite direction. When the area of ​​the first side portion 321 in a plan view is constant, the length of the first supply slit 34 having the bent portion 341 tends to be longer than the length of the first supply slit without the bent portion 341. This tends to increase the electrical resistance of the first supply slit 34. This tends to decrease the shunt current. When the length of the first supply slit 34 is constant, the first supply slit 34 having the bent portion 341 has higher flow resistance and electrical resistance than the first supply slit without the bent portion 341. The bent portion 341 may be configured, for example, so that the flow direction of the electrolyte changes from either the left or right direction along the length of the first side portion 321 to the opposite direction. The bent portion 341 may be configured so that the flow direction of the electrolyte changes from either an upward or downward direction along a direction perpendicular to the longitudinal direction of the first side portion 321 to the opposite direction.

[0038] The number of the bent portion 341 may be singular or plural. When the number of the bent portion 341 is singular, the bent portion 341 may be configured to change, for example, from a rightward direction to a leftward direction. Furthermore, the bent portion 341 may be configured to change the flow direction of the electrolyte solution from a downward direction to an upward direction along a direction perpendicular to the longitudinal direction of the first side portion 321. When the number of the bent portion 341 is plural, the bent portion 341 may have, for example, a first bent portion configured to change the flow direction of the electrolyte solution from a rightward direction to a leftward direction along the longitudinal direction of the first side portion 321, and a second bent portion configured to change the flow direction from a leftward direction to a rightward direction. Furthermore, the bent portion 341 may have, for example, a first bent portion configured to change the flow direction of the electrolyte solution from an upward direction to a downward direction along a direction perpendicular to the longitudinal direction of the first side portion 321, and a second bent portion configured to change the flow direction from a downward direction to an upward direction. The first bent portion and the second bent portion are arranged in the order in which the electrolyte flows.

[0039] In this example, there is only one bent portion 341. The bent portion 341 in this example is configured so that the flow direction of the electrolyte changes from a rightward direction to a leftward direction along the length of the first side portion 321. The first supply slit 34 in this example has, in order of electrolyte flow, a first straight path 34a, a bent portion 341, a second straight path 34b, a corner portion 34c, and a third straight path 34d. The first straight path 34a extends rightward from the first supply manifold 33 along the length of the first side portion 321. The bent portion 341 connects the right end of the first straight path 34a and the right end of the second straight path 34b and turns back from the rightward direction to the leftward direction. The second straight path 34b extends leftward from the bent portion 341 along the length of the first side portion 321. The corner portion 34c bends upward from the left end of the second straight path 34b. When the length of the first supply slit 34 is constant, the first supply slit 34 having the corner portion 34c has higher flow resistance and electrical resistance than a first supply slit without the corner portion 34c. The third straight path 34d extends from the upper end of the corner portion 34c toward the inner peripheral edge 32i in a direction perpendicular to the longitudinal direction of the first side portion 321.

[0040] The first exhaust manifold 35 is an outlet for the first fluid. The first fluid includes oxygen gas generated by electrolysis of water, which will be described later. The first exhaust manifold 35 is a through-hole that penetrates the first main surface and the second main surface of the frame 32. In this example, the first exhaust manifold 35 is provided to the right of the second side portion 322.

[0041] The first discharge slit 36 ​​is a flow path that allows the first fluid to flow toward the first discharge manifold 35. The first discharge slit 36 ​​is a flow path that guides the first fluid from the inner peripheral edge 32i of the frame 32 to the first discharge manifold 35. The first discharge slit 36 ​​is a groove having a bottom surface. The first discharge slit 36 ​​is provided on the first main surface of the frame 32 so as to connect the inner peripheral edge 32i of the frame 32 and the first discharge manifold 35.

[0042] The electrical resistance of the first exhaust slit 36 ​​may be the same as or different from that of the first supply slit 34. The total electrical resistance of the first supply slit 34 and the first exhaust slit 36 ​​may be 25 Ω or more and 500 Ω or less. The width and length of the first exhaust slit 36 ​​may be the same as or different from those of the first supply slit 34. Like the first supply slit 34, the first exhaust slit 36 ​​has a bent portion 361 that is folded back. The significance of the bent portion 361 is the same as that of the bent portion 341. Oxygen gas generated by water electrolysis tends to accumulate in the bent portion 361. Because oxygen gas has a lower electrical conductivity than the electrolyte, accumulation of oxygen gas in the bent portion 361 tends to increase the electrical resistance of the first exhaust slit 36. Therefore, the shunt current tends to decrease, and the loss rate due to the shunt current tends to be reduced. The shape of the first exhaust slit 36 ​​in this example is the same as that of the first supply slit 34. In a plan view of the frame 32, the first supply slit 34 connects from the first supply manifold 33 on the left side of the first side 321 to the center of the lower edge of the inner peripheral edge 32i, and the first discharge slit 36 ​​connects from the first discharge manifold 35 on the right side of the second side 322 to the center of the upper edge of the inner peripheral edge 32i. Therefore, the flow path between the first supply manifold 33 and the first discharge manifold 35 tends to be long.

[0043] The second exhaust manifold 37 is an outlet for the second fluid. The second fluid includes hydrogen gas generated by electrolysis of water. The second exhaust manifold 37 is a through-hole that penetrates the first main surface and the second main surface of the frame 32. In this example, the second exhaust manifold 37 is provided on the left side of the second side portion 322.

[0044] The second discharge slit (not shown) is a flow path that allows the second fluid to flow toward the second discharge manifold 37. The second discharge slit is a flow path that guides the second fluid from the inner peripheral edge 32i of the frame 32 to the second discharge manifold 37. The second discharge slit is a groove having a bottom surface. The second discharge slit is provided on the second main surface of the frame 32 so as to connect the inner peripheral edge 32i of the frame 32 and the second discharge manifold 37.

[0045] The seal groove is provided near the outer peripheral edge 32e of at least one of the first and second main surfaces of the frame 32. The seal groove is annularly provided so as to surround all of the manifolds 33, 35, 37 and the slits 34, 36. The manifolds 33, 35, 37 and the slits 34, 36 are located in the area between the inner peripheral edge of the seal groove and the inner peripheral edge 32i. A seal member (not shown) is placed in the seal groove. The seal member prevents the electrolyte from leaking outside the stack 2a. The seal member is, for example, an annular rubber member.

[0046] In this example, the frame 32 does not have a second supply manifold and a second supply slit, but may have a second supply manifold and a second supply slit. The second supply manifold is a supply port for the electrolytic solution. The second supply manifold is a through hole penetrating the first and second main surfaces of the frame 32. The second supply slit is a flow path through which the electrolytic solution supplied from the second supply manifold flows. The electrolytic solution supplied from the second supply manifold is the same as the electrolytic solution supplied from the first supply manifold 33. The second supply slit is a flow path that guides the electrolytic solution from the second supply manifold to the inner peripheral edge 32i of the frame 32. The second supply slit is a groove having a bottom surface. The second supply slit is provided on the second main surface of the frame 32 so as to connect the second supply manifold and the inner peripheral edge 32i of the frame 32.

[0047] [Hydrogen Production Apparatus] A hydrogen production apparatus 1 according to an embodiment will be described with reference to Figures 2 and 3. The hydrogen production apparatus 1 produces hydrogen by electrolyzing water contained in a supplied electrolytic solution. The hydrogen production apparatus 1 generates oxygen in addition to producing hydrogen through the electrolysis of water. The hydrogen production apparatus 1 can also be used as an apparatus for producing oxygen. The hydrogen production apparatus 1 includes a cell stack 2 having a plurality of electrolysis cells 20. In Figure 2, only the appearance of the separator 3 of the electrolysis cell 20 is shown. For ease of explanation, in Figure 2, the separator 3, first current collector plate 41, second current collector plate 42, supply / discharge plate 5, folding plate 6, first end plate 91, and second end plate 92 of the electrolysis cell 20 are hatched.

[0048] [Electrolytic Cell] As shown in FIG. 3 , each electrolytic cell 20 includes an anion exchange membrane (AEM) 21, an anode 22, and a cathode 23. That is, the hydrogen production device 1 is an AEM-type hydrogen production device. The anion exchange membrane 21 is disposed between the anode 22 and the cathode 23. A known anion exchange membrane can be used for the anion exchange membrane 21. The anode 22 includes an anode catalyst 221 and an anode diffusion layer 222. The cathode 23 includes a cathode catalyst 231 and a cathode diffusion layer 232. Known materials can be used for the anode catalyst 221, the anode diffusion layer 222, the cathode catalyst 231, and the cathode diffusion layer 232. Each electrolysis cell 20 is configured by stacking an anode diffusion layer 222, an anode catalyst 221, an anion exchange membrane 21, a cathode catalyst 231, and a cathode diffusion layer 232 in this order. The anode catalyst 221, the anion exchange membrane 21, and the cathode catalyst 231 may be bonded together to form a catalyst coated membrane (CCM), or the anode diffusion layer 222, the anode catalyst 221, the anion exchange membrane 21, the cathode catalyst 231, and the cathode diffusion layer 232 may be bonded together to form a membrane electrode assembly (MEA). All of the electrolysis cells 20 are electrically connected in series. The electrolysis cells 20 are usually configured inside a cell stack 2.

[0049] 2 , the cell stack 2 of this example includes a laminate 2a, a first current collecting plate 41 and a second current collecting plate 42, a first end plate 91 and a second end plate 92, and a clamping mechanism 93. The cell stack 2 is configured by sandwiching the laminate 2a and the first current collecting plate 41 and the second current collecting plate 42 between the first end plate 91 and the second end plate 92 from both sides in the stacking direction, and clamping the first end plate 91 and the second end plate 92 with the clamping mechanism 93. The cell stack 2 of this example further includes a supply / discharge plate 5 and a folding plate 6.

[0050] The number of electrolytic cells 20 is not particularly limited and can be selected appropriately. The greater the number of electrolytic cells 20, the greater the amount of hydrogen produced. The number of electrolytic cells 20 is, for example, 15 or more. A cell stack 2 having 15 or more electrolytic cells 20 can increase the amount of hydrogen produced. However, the greater the number of electrolytic cells 20, the greater the loss rate due to shunt current. The number of electrolytic cells 20 is, for example, 200 or less. A cell stack 2 having 200 or less electrolytic cells 20 is likely to reduce the loss rate due to shunt current. Furthermore, a cell stack 2 having 200 or less electrolytic cells 20 is likely to be compact because the length of the stack 2a along the stacking direction can be easily shortened. The number of electrolytic cells 20 may be 20 to 150, 30 to 125, or 35 to 100.

[0051] [First Current Collector Plate and Second Current Collector Plate] The first current collector plate 41 and the second current collector plate 42 cause water electrolysis, which will be described later, when a voltage is applied between the two current collector plates 41, 42 from a power source (not shown). The first current collector plate 41 is disposed between the laminate 2a and the first end plate 91. The second current collector plate 42 is disposed between the laminate 2a and the second end plate 92. The first current collector plate 41 and the second current collector plate 42 are formed of a metal. The metal forming the first current collector plate 41 and the second current collector plate 42 is, for example, copper or a copper alloy.

[0052] [Supply / Discharge Plate] The supply / discharge plate 5 supplies the electrolytic solution to the plurality of electrolytic cells 20 and discharges fluids from the plurality of electrolytic cells 20. For this purpose, a pipe 7 described below is connected to the supply / discharge plate 5. The fluids are the first fluid and the second fluid.

[0053] The supply and discharge plate 5 is disposed at least between the first current collector plate 41 and the first end plate 91 and between the second current collector plate 42 and the second end plate 92. In this example, the supply and discharge plate 5 is disposed between the first current collector plate 41 and the first end plate 91, but is not disposed between the second current collector plate 42 and the second end plate 92. In this example, a folding plate 6 (described later) is disposed between the second current collector plate 42 and the second end plate 92. The supply and discharge plate 5 is adjacent to the first current collector plate 41 and the first end plate 91. The folding plate 6 is adjacent to the second current collector plate 42 and the second end plate 92. In the cell stack 2 of this example, the first end plate 91, the supply and discharge plate 5, the first current collector plate 41, the stack 2a, the second current collector plate 42, the folding plate 6, and the second end plate 92 are arranged in this order.

[0054] Although not shown, the supply / discharge plate 5 of this example has a first supply communication hole, a first discharge communication hole, and a second discharge communication hole that communicate with the first supply manifold 33, the first discharge manifold 35, and the second discharge manifold 37, respectively. These communication holes penetrate the first and second main surfaces of the supply / discharge plate 5. The first main surface is the surface that faces the stack 2a. The second main surface is the surface opposite the first main surface and faces the first end plate 91.

[0055] In this example, the supply / discharge plate 5 does not have a second supply passage communicating with the second supply manifold because the separator 3 does not have a second supply manifold. Unlike this example, if the separator 3 has a second supply manifold, the supply / discharge plate 5 may have a second supply passage. The second supply passage penetrates the first main surface and the second main surface of the supply / discharge plate 5.

[0056] The material of the supply / discharge plate 5 is resin. The resin forming the supply / discharge plate 5 is an electrically insulating resin. The supply / discharge plate 5 formed from such a resin also functions as a member that electrically insulates between the first end plate 91 and the first current collector plate 41. The resin forming the supply / discharge plate 5 may be formed from a resin that has at least one of alkali resistance and heat resistance in addition to electrical insulation. For the resin forming the supply / discharge plate 5, refer to the description of the resin forming the frame 32 of the separator 3. The resin forming the supply / discharge plate 5 may be the same as or different from the resin forming the frame 32.

[0057] (Folding Plate) The folding plate 6 folds the electrolytic solution supplied from the supply / discharge plate 5 and returns it to the supply / discharge plate 5. The piping 7, which will be described later, is not connected to the folding plate 6. The folding plate 6 is not the supply / discharge plate 5 that supplies the electrolytic solution and discharges the gas generated by the electrolysis of water contained in the electrolytic solution. The folding plate 6 does not have a hole through which the electrolytic solution is supplied from outside the cell stack 2 and a hole through which the gas is discharged to outside the cell stack 2. The folding plate 6 in this example is disposed between the second current collector plate 42 and the second end plate 92. Unlike this example, the supply / discharge plate 5 may be disposed between the second current collector plate 42 and the second end plate 92, and the folding plate 6 may be disposed between the first current collector plate 41 and the first end plate 91. The folding plate 6 has a first main surface and a second main surface. The first main surface faces the second current collector plate 42. The second main surface is the surface opposite to the first main surface and faces the second end plate 92. The first main surface has a flow path that guides the first fluid to the first discharge manifold 35 or a flow path that guides the second fluid to the second discharge manifold 37. The folding plate 6 may include a conductive plate (not shown) and a frame body, similar to the separator 3. The flow paths (not shown) are provided on the first and second main surfaces of the frame body.

[0058] The resin forming the frame of the folding plate 6 is an electrically insulating resin. The frame of the folding plate 6 formed from such a resin also functions as a member that electrically insulates between the second end plate 92 and the second current collector plate 42. The resin forming the frame of the folding plate 6 may be formed from a resin that is electrically insulating and has at least one of alkali resistance and heat resistance. For the resin forming the frame of the folding plate 6, refer to the description of the resin forming the frame 32 of the separator 3. The resin forming the frame of the folding plate 6 may be the same as or different from the resin forming the supply / discharge plate 5. Unlike this example, the folding plate 6 may not include a conductive plate and may be formed from a resin.

[0059] [Piping] The cell stack 2 includes a distribution system, which includes a pipe 7 and a pump (not shown).

[0060] The piping 7 includes a supply pipe connecting a supply source (not shown) to the cell stack 2, and a discharge pipe connecting the cell stack 2 to a storage tank (not shown). The supply source has a first supply source that stores an electrolyte. In this example, the supply source does not have a second supply source that stores an electrolyte, but may further have a second supply source. The storage tank has a first storage tank that stores the generated oxygen gas and a second storage tank that stores the generated hydrogen gas.

[0061] The supply pipe in this example includes a first supply pipe 71 but does not include a second supply pipe. The first supply pipe 71 carries the electrolytic solution supplied to the anode 22. The first supply pipe 71 passes through a first supply hole in a first end plate 91 (described later) and connects a first supply source to a first supply hole in the supply / discharge plate 5. The second supply pipe carries the electrolytic solution supplied to the cathode 23. The second supply pipe passes through a second supply hole in the first end plate 91 and connects a second supply source to a second supply hole in the supply / discharge plate 5. The second supply hole in the first end plate 91 communicates with the second supply hole in the supply / discharge plate 5. The second supply pipe is inserted through the second supply hole in the first end plate 91. In this example, the separator 3 does not include a second supply manifold, and the supply / discharge plate 5 does not include a second supply hole. Therefore, the first end plate 91 does not include a second supply hole. However, if the separator 3 has a second supply manifold and the supply / discharge plate 5 has a second supply passage, the supply pipe may have a second supply pipe.

[0062] The discharge pipes include a first discharge pipe 72 and a second discharge pipe 73. For convenience of explanation, FIG. 2 shows the first discharge pipe 72 and the second discharge pipe 73 arranged in parallel in the up-down direction, but the first discharge pipe 72 and the second discharge pipe 73 are actually arranged in parallel in the depth direction of the paper in FIG. 2 . The first fluid flows through the first discharge pipe 72. The first discharge pipe 72 passes through a first discharge communication hole in a first end plate 91 (described later) and connects the first discharge communication hole in the supply / discharge plate 5 to the first storage tank. The second discharge pipe 73 passes through a second discharge communication hole in the first end plate 91 (described later) and connects the second discharge communication hole in the supply / discharge plate 5 to the second storage tank.

[0063] The connection points of the first supply pipe 71, the first discharge pipe 72, and the second discharge pipe 73 with the supply / discharge plate 5 may be formed as cylindrical portions that are integrated into the supply / discharge plate 5 in advance. In a structure in which separately prepared piping is connected to this cylindrical portion, it is easy for an operator to handle long piping, and the connection work is therefore easy.

[0064] The pump pressure-feeds the electrolytic solution to the plurality of electrolytic cells 20. The pump is provided midway along the first supply pipe 71.

[0065] [First End Plate / Second End Plate] The first end plate 91 and the second end plate 92 sandwich the first current collector plate 41 and the second current collector plate 42 from the outside of the first current collector plate 41 and the second current collector plate 42. The first end plate 91 and the second end plate 92 are made of metal. The first end plate 91 and the second end plate 92 made of metal have higher rigidity than end plates made of resin. This makes it easier to maintain the fastened state of the laminate 2a over a long period of time. The metal used to form the first end plate 91 and the second end plate 92 is, for example, steel or nickel. The steel may be any of various types, such as stainless steel or carbon steel.

[0066] Although not shown, the first end plate 91 of this example has a first supply communication hole, a first discharge communication hole, and a second discharge communication hole. The first supply communication hole, the first discharge communication hole, and the second discharge communication hole penetrate the first main surface and the second main surface of the first end plate 91. The first supply communication hole of the first end plate 91 communicates with the first supply communication hole of the supply / discharge plate 5. The first supply pipe 71 is inserted through the first supply communication hole of the first end plate 91. The first discharge communication hole of the first end plate 91 communicates with the first discharge communication hole of the supply / discharge plate 5. The first discharge pipe 72 is inserted through the first discharge communication hole of the first end plate 91. The second discharge communication hole of the first end plate 91 communicates with the second discharge communication hole of the supply / discharge plate 5. The second discharge pipe 73 is inserted through the second discharge communication hole of the first end plate 91 .

[0067] [Clamping Mechanism] The clamping mechanism 93 clamps the first end plate 91 and the second end plate 92 toward each other. The clamping mechanism 93 clamps the first end plate 91 and the second end plate 92 together, maintaining the stacked state of the electrolysis cells 20. The clamping mechanism 93 in this example includes multiple rods 94 and, although not shown, nuts attached to both ends of each rod 94. Tightening both nuts narrows the gap between the first end plate 91 and the second end plate 92. Each rod 94 penetrates the first end plate 91 and the second end plate 92. In this example, each rod 94 does not penetrate any component disposed between the first end plate 91 and the second end plate 92. Unlike this example, each rod 94 may penetrate at least one component disposed between the first end plate 91 and the second end plate 92. In this case, the size of the member through which the rod 94 passes, as viewed from the stacking direction of the stack 2a, is larger than the size of the member that the rod 94 does not pass through, as viewed from the stacking direction of the stack 2a. Each rod 94 and each nut is made of metal. The metal forming each rod 94 and each nut is, for example, steel or titanium. The steel may be any of various types, such as stainless steel.

[0068] [Electrolyte] The electrolyte is an alkaline aqueous solution. The alkaline aqueous solution may be, for example, potassium hydroxide (KOH) or sodium bicarbonate (NaHCO ３) dissolved in water. When the electrolyte is an alkaline aqueous solution, the electrolysis of water is promoted compared to when the fluid supplied to the electrolytic cell 20 is pure water. The concentration of the electrolyte in the alkaline aqueous solution is, for example, 0.1 mass% or more and 10 mass% or less, when the entire alkaline aqueous solution is taken as 100 mass%. The concentration of the electrolyte in the alkaline aqueous solution may be 0.5 mass% or more and 8 mass% or less, or 1.0 mass% or more and 6.0 mass% or less. The pH value of the alkaline aqueous solution is, for example, 8 or more and 15 or less. The pH value of the alkaline aqueous solution may be 10 or more and 14.3 or less. The electrical conductivity of the alkaline aqueous solution is, for example, 0.003 mS / cm or more and 500 mS / cm or less. The electrical conductivity of the alkaline aqueous solution may be 0.01 mS / cm or more and 400 mS / cm or less, or 0.02 mS / cm or more and 300 mS / cm or less.

[0069] [Electrolysis] An electrolyte is supplied to each anode 22 through the first supply pipe 71. In this example, no electrolyte is supplied to each cathode 23 from the first supply pipe 71. Water moves from each anode 22 side to each cathode 23 through the anion exchange membrane 21. When a voltage is applied between the first current collector plate 41 and the second current collector plate 42 by a power source (not shown), the following electrochemical reaction occurs: Anode: 4OH － →2H ２ O+O ２ +4e － Cathode: 4H ２ O+4e － →2H ２ +4OH －

[0070] At each anode 22, hydroxide ions (OH －) generates water and oxygen and releases electrons. At each cathode 23, water and electrons combine to generate hydrogen and hydroxide ions. The generated hydroxide ions pass through the anion exchange membrane 21 and move from the cathode 23 to the anode 22. Oxygen gas generated at the anode 22 is discharged from the cell stack 2 through the first discharge pipe 72. Hydrogen gas generated at the cathode 23 is discharged from the cell stack 2 through the second discharge pipe 73. The fluid discharged from the first discharge pipe 72 may contain water generated at the anode 22 and unreacted electrolyte solution supplied to the anode 22. The fluid discharged from the second discharge pipe 73 may contain unreacted water that moved to the cathode 23.

[0071] Unlike this example, the cell stack 2 may be any one of the following forms (A) to (C): (A) No supply / discharge plate 5 and no turning-back plate 6. (B) A supply / discharge plate 5 is provided, but no turning-back plate 6 is provided. (C) A supply / discharge plate 5 is not provided, but a turning-back plate 6 is provided.

[0072] In the case of the above-described configuration (A), the separator 3 at the end adjacent to the first current collector plate 41 (hereinafter referred to as the first separator 3) also serves as a supply / discharge plate, and the separator 3 at the end adjacent to the second current collector plate 42 (hereinafter referred to as the second separator 3) also serves as a folding plate. The piping 7 is directly connected to the frame 32 of the first separator 3. That is, each of the pipes 71, 72, and 73 may be directly connected to the frame 32 of the first separator 3 so that the inside of the first supply pipe 71 communicates with the first supply manifold 33, the inside of the first discharge pipe 72 communicates with the first discharge manifold 35, and the inside of the second discharge pipe 73 communicates with the second discharge manifold 37. The pipes 71, 72, and 73 may be welded to the frame 32 using, for example, an organic solvent. The second separator 3 has a flow path that prevents the fluid supplied to the cell stack 2 from flowing out of the cell stack 2 and turns back toward the first end plate 91. Between the first end plate 91 and the first current collector plate 41, and between the second end plate 92 and the second current collector plate 42, an insulating material that electrically insulates the first end plate 91 from the first current collector plate 41 and the second end plate 92 from the second current collector plate 42 may be provided.

[0073] In the case of the above-mentioned form (B), the second separator 3 also serves as a folding plate. The second separator 3 prevents the fluid supplied to the cell stack 2 from flowing out of the cell stack 2, and has a flow path that folds back toward the first end plate 91. The above-mentioned insulating material may be provided between the second end plate 92 and the second current collector plate 42.

[0074] In the case of the above-mentioned form (C), the first separator 3 also serves as a supply / discharge plate. The pipe 7 is directly connected to the frame 32 of the first separator 3. The above-mentioned insulating material may be provided between the first end plate 91 and the first current collector plate 41.

[0075] <<Example of Trial Calculation>> In the example of trial calculation, the difference in the loss rate based on the shunt current caused by the difference in the electrical resistance value of the first supply slit was investigated.

[0076] [Model No. 1 to Model No. 25, Model No. 101 to Model No. 110] The catalyst area, current density, number of stacked electrolytic cells, and electrical resistance value of the first supply slit for each model are as shown in Table 1. In Table 1, the number of stacked electrolytic cells is shown as "Number of stacked electrolytic cells," and the electrical resistance value of the first supply slit is shown as "Electrical resistance value." The catalyst area is the area of ​​each of the anode catalyst and the cathode catalyst. The electrical resistance value of the first supply slit is the value obtained by dividing the length of the first supply slit by the cross-sectional area of ​​the first supply slit, and then dividing this value by the conductivity of the electrolytic solution flowing through the first supply slit.

[0077] The power, loss based on shunt current, and loss rate based on shunt current for each model are shown in Table 1. The power for each model is the product of the catalyst area, current density, voltage, and the number of stacked electrolysis cells. The voltage in this example was 1.8 V. The loss for each model is calculated as Ik ２×Rs. Ik=[(k−(N+1) / 2){Va+Vc+I(Rcon+Rct+Rdif)}] / Rs where Ik: shunt current flowing from the kth electrolytic cell to the first supply manifold, N: number of electrolytic cells, Va: anode voltage, Vc: cathode voltage, I: current flowing through all electrolytic cells, Rcon (conduction resistance): conductive resistance, Rct (charge transfer resistance): charge transfer resistance, Rdif (diffusion resistance): diffusion resistance, Rs: electrical resistance of the first supply slit. The loss rate for each model is the loss divided by power, expressed as a percentage.

[0078]

[0079] As shown in Table 1, when the catalyst area, current density, number of layers, and power were the same, Models 1 to 5, each with a first supply slit electrical resistance of 50 Ω, had a lower loss rate than Models 101 to 105, each with a first supply slit electrical resistance of 30 Ω. Comparing Models 11 to 25 with the same catalyst area, the higher the electrical resistance, the lower the loss rate. Comparing Models 21 to 25 with Models 106 to 110 with the same catalyst area, the difference in loss rate between the former and latter was 0.01% to 0.06%. Meanwhile, the length of the first supply slit in Models 106 to 110 was 10% or more longer than the length of the first supply slit in Models 21 to 25. Increasing the length of the first supply slit increases the pressure loss due to increased flow resistance and the size of the electrolytic cell due to an increased frame area. When the electrical resistance is 1000 Ω or less, the increase in pressure loss is smaller than when the electrical resistance is greater than 1000 Ω, and the electrolytic cell is more likely to be small.

[0080] REFERENCE SIGNS LIST 1 Hydrogen production device 2 Cell stack 2a Stacked body 20 Electrolysis cell 21 Anion exchange membrane 22 Anode 221 Anode catalyst 222 Anode diffusion layer 23 Cathode 231 Cathode catalyst 232 Cathode diffusion layer 3 Separator 31 Conductive plate 32 Frame 32e Outer peripheral edge portion 32i Inner peripheral edge portion 321 First side portion 322 Second side portion 323 Third side portion 324 Fourth side portion 33 First supply manifold 34 First supply slit 341 Bent portion 34a First straight path 34b Second straight path 34c Corner portion 34d Third straight path 35 First exhaust manifold 36 First exhaust slit 361 Bent portion 37 Second exhaust manifold 41 First current collector plate 42 Second current collector plate 5 Supply and discharge plate, 6 Turning plate 7 Piping 71 First supply pipe, 72 First discharge pipe, 73 Second discharge pipe 91 First end plate, 92 Second end plate 93 Fastening mechanism, 94 Rod D Shortest distance, L Minimum length

Claims

1. A separator for use in an electrolytic cell equipped with an anion exchange membrane, the separator comprising: a conductive plate; and a frame supporting an outer peripheral edge of the conductive plate, the frame being made of an electrically insulating resin material, the frame having a supply manifold serving as a supply port for an electrolytic solution, and a supply slit connecting the supply manifold with an inner peripheral edge of the frame, the supply slit having an electrical resistance value of 50 Ω or more and 1000 Ω or less, the electrical resistance value being the value obtained by dividing the length of the supply slit by the cross-sectional area of ​​the supply slit and then dividing it by the conductivity of the electrolytic solution flowing through the supply slit.

2. The separator according to claim 1, wherein the supply slit has a folded-back bent portion.

3. A separator according to claim 1 or claim 2, wherein the frame has an exhaust manifold which is an exhaust port for gas generated by electrolysis of water contained in the electrolyte, and an exhaust slit which connects the exhaust manifold with the inner peripheral edge, and the exhaust slit has a bent portion which is folded back.

4. An electrolytic cell comprising the separator according to any one of claims 1 to 3, an anode, an anion exchange membrane, and a cathode.

5. A cell stack comprising the electrolysis cell according to claim 4.

6. A hydrogen production device comprising the cell stack according to claim 5.

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