Water electrolysis cell

Abstract

To provide a water electrolytic cell that can suppress the deformation of a separator.SOLUTION: A water electrolytic cell comprises a separator with grooves on the front and back sides that become channels, the separator has an oxygen electrode side supply hole, an oxygen electrode side discharge hole, a hydrogen electrode side supply hole, a hydrogen electrode side discharge hole, an intercellular channel supply hole, and an intercellular channel discharge hole at the edge of the separator in a plane view, a seal member enclosing the oxygen electrode side supply hole, and a seal member enclosing the oxygen electrode side discharge hole are arranged in a plane view of the separator, and no seal members surrounding the respective holes are arranged on the hydrogen electrode side supply hole, the hydrogen electrode side discharge hole, the intercellular channel supply hole, and the intercellular channel discharge hole.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a water electrolysis cell.

Background Art

[0002] Various studies have been conducted on water electrolysis devices. For example, in Patent Document 1, a technique for suppressing the lifting of an electrode part by disposing a load applying mechanism for pressing inside a water electrolysis cell in a differential pressure type high-pressure water electrolysis device is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to boost the hydrogen generated by water electrolysis, there is a need to increase the pressure inside the water electrolysis cell (hereinafter sometimes referred to as a cell). In conventional cells, there is a problem that the separator of the cell is deformed by a load applying mechanism. In order to suppress the deformation of the separator, if the separator is made thicker, there is a problem that the weight of the cell increases.

[0005] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide a water electrolysis cell capable of suppressing the deformation of a separator.

Means for Solving the Problems

[0006] In the present disclosure, there is provided a water electrolysis cell, wherein the water electrolysis cell includes a separator having grooves serving as flow paths on the front and back surfaces, The separator has, in a plan view, an oxygen electrode side supply hole, an oxygen electrode side discharge hole, a hydrogen electrode side supply hole, a hydrogen electrode side discharge hole, an inter-cell flow path supply hole, and an inter-cell flow path discharge hole at end portions in the plane direction. Provided is a water electrolysis cell in which, in a plan view of the separator, a seal member surrounding the oxygen electrode side supply hole and a seal member surrounding the oxygen electrode side discharge hole are disposed, and no seal member surrounding each of the holes is disposed in the hydrogen electrode side supply hole, the hydrogen electrode side discharge hole, the inter-cell flow path supply hole, and the inter-cell flow path discharge hole.

[0007] In the present disclosure, the water electrolysis cell may include an electrode part, a support frame having an opening surrounding the electrode part, and a pair of the separators sandwiching the electrode part and the support frame.

Advantages of the Invention

[0008] The water electrolysis cell of the present disclosure can suppress deformation of the separator.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments according to the present disclosure will be described. Note that matters other than those specifically mentioned in this specification and necessary for implementing the present disclosure (for example, general configurations and manufacturing processes of water electrolysis cells that do not characterize the present disclosure) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the content disclosed in this specification and common general knowledge in the relevant field. Also, the dimensional relationships (length, width, thickness, etc.) in the figures do not reflect the actual dimensional relationships. In this specification, "~" indicating a numerical range is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value. Also, any combination can be adopted for the upper limit value and the lower limit value in the numerical range.

[0011] In the present disclosure, there is provided a water electrolysis cell, wherein the water electrolysis cell includes a separator having grooves serving as flow paths on the front and back surfaces, the separator has, at the end portions in the plane direction in plan view, an oxygen electrode side supply hole, an oxygen electrode side discharge hole, a hydrogen electrode side supply hole, a hydrogen electrode side discharge hole, an inter-cell flow path supply hole, and an inter-cell flow path discharge hole, in the plan view of the separator, a seal member surrounding the oxygen electrode side supply hole and a seal member surrounding the oxygen electrode side discharge hole are arranged, and seal members surrounding the respective holes are not arranged in the hydrogen electrode side supply hole, the hydrogen electrode side discharge hole, the inter-cell flow path supply hole, and the inter-cell flow path discharge hole, and there is provided a water electrolysis cell.

[0012] FIG. 1 is a partial cross-sectional schematic view showing an example of a part of a water electrolysis cell for explaining the problems of a conventional water electrolysis cell. As shown in FIG. 1, a conventional water electrolysis cell 100 includes an anode separator 10, an anode side gas diffusion layer 11, an anode side microporous layer 12, an anode catalyst layer 13, an electrolyte membrane 14, a cathode catalyst layer 15, a cathode side microporous layer 16, a cathode side gas diffusion layer 17, a cathode separator 18, and a support frame 19.

[0013] FIG. 2 is a plan schematic view showing an example when a conventional water electrolysis cell is viewed in plan. As shown in FIG. 2, a separator 60 of a conventional water electrolysis cell has an oxygen electrode side supply hole 20, an oxygen electrode side discharge hole 21, a hydrogen electrode side supply hole 30, a hydrogen electrode side discharge hole 31, an inter-cell flow path supply hole 40, and an inter-cell flow path discharge hole 41 at the end portions in the plane direction. In the separator 60, the oxygen electrode side supply hole 20, the oxygen electrode side discharge hole 21, the hydrogen electrode side supply hole 30, the hydrogen electrode side discharge hole 31, the inter-cell flow path supply hole 40, and the inter-cell flow path discharge hole 41 are surrounded by the outer peripheral seal member 50. Further, the oxygen electrode side supply hole 20, the oxygen electrode side discharge hole 21, the hydrogen electrode side supply hole 30, and the hydrogen electrode side discharge hole 31 are each surrounded by a seal member 51. The material of the outer peripheral seal member 50 and the material of the seal member 51 may be the same or different.

[0014] As shown in FIG. 2, in a conventional cell used as a fuel cell, since it is necessary to seal the flow paths of three fluids, i.e., hydrogen, an oxygen-containing gas such as oxygen or air, and a cooling medium, respectively, each space is independent. In order to increase the pressure of the hydrogen to be extracted, as shown on the left side of FIG. 1, when the pressure of the hydrogen electrode is increased, a differential pressure is generated between the inside and between the cells, and the anode separator 10 is deformed. As shown on the right side of FIG. 1, since the support frame 19 is pulled due to the deformation of the anode separator 10, the seal of the support frame 19 is peeled off from the electrolyte membrane 14, leading to a problem of leakage.

[0015] FIG. 3 is a schematic plan view showing an example of the water electrolysis cell of the present disclosure when viewed in plan. The same components as those in FIG. 2 in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 3, in the separator 70 of the water electrolysis cell of the present disclosure, the oxygen electrode side supply hole 20 and the oxygen electrode side discharge hole 21 are each surrounded by a seal member 51. On the other hand, the hydrogen electrode side supply hole 30 and the hydrogen electrode side discharge hole 31 are not each surrounded by a seal member 51, and the spaces of the cathode fluid flow path and the cooling medium flow path are connected.

[0016] In the present disclosure, by not arranging seal members surrounding the respective holes in the hydrogen electrode side supply hole and the hydrogen electrode side discharge hole serving as the hydrogen electrode manifold, and the inter-cell flow path supply hole and the inter-cell flow path discharge hole serving as the cooling medium manifold of the cooling medium flow path between the cells, the spaces of the cathode fluid flow path and the cooling medium flow path are connected, the hydrogen electrodes between the cells and inside the cells are made to have the same pressure, deformation of the separator can be suppressed, and the occurrence of leakage can be suppressed. In addition, in the present disclosure, by using a separator having a flow path for a cooling medium, the cooling medium can be made to flow into the cell, heat generation in the cell can be suppressed, and the durability of the cell, the seal member, etc. can be improved. Further, a conventional cell for a fuel cell can be diverted and used as a water electrolysis cell, and cost reduction can be achieved.

[0017] The water electrolysis cell of the present disclosure electrolyzes water supplied to the anode (oxygen electrode), oxygen is generated from the anode, and hydrogen is generated from the cathode (hydrogen electrode) as follows. Anode: H2O → 2H + + 1 / 2O2 + 2e - Cathode: 2H + + 2e - → H2

[0018] The water electrolysis cell of the present disclosure may be configured such that a plurality of the water electrolysis cells are stacked to form a water electrolysis cell stack (hereinafter sometimes referred to as a stack). The number of stacked water electrolysis cells is not particularly limited, and may be, for example, 2 to several hundreds. The water electrolysis cell of the present disclosure may include a separator, and generally may include an electrode portion, a support frame having an opening surrounding the electrode portion, and a pair of separators sandwiching the electrode portion and the support frame.

[0019] One of the pair of separators is an anode separator and the other is a cathode separator. The anode separator and the cathode separator are collectively referred to as a separator. The two separators, the anode separator and the cathode separator, sandwich the electrode portion and the support frame. The separator has holes serving as a manifold such as supply holes and discharge holes for allowing fluids such as reaction water, oxygen, hydrogen, and a cooling medium to flow in the stacking direction of the water electrolysis cell. As the reaction water and the cooling medium, water, pure water, alkaline water, etc. can be used. Specifically, in a plan view, the separator has an oxygen electrode side supply hole, an oxygen electrode side discharge hole, a hydrogen electrode side supply hole, a hydrogen electrode side discharge hole, an inter-cell flow path supply hole, and an inter-cell flow path discharge hole at the end portions in the plane direction. The oxygen electrode side supply hole supplies reactive water to the oxygen electrode. The oxygen electrode side discharge hole discharges oxygen generated by water electrolysis from the oxygen electrode. The hydrogen electrode side supply hole may not be used during water electrolysis, and a cooling medium may be supplied to the hydrogen electrode. The hydrogen electrode side discharge hole discharges hydrogen generated by water electrolysis from the hydrogen electrode. The inter-cell flow path supply hole supplies a cooling medium between cells of the water electrolysis cell stack. The inter-cell flow path discharge hole discharges a cooling medium from between cells of the water electrolysis cell stack.

[0020] The separator has grooves serving as flow paths on the front and back surfaces. Specifically, the separator may have flow paths for reactive fluids such as reactive water, oxygen, and hydrogen on the surface in contact with the gas diffusion layer. Further, the separator may have a flow path for a cooling medium for keeping the temperature of the water electrolysis cell constant between cells, that is, on the surface opposite to the surface in contact with the gas diffusion layer. The anode separator may have flow paths for anode fluids such as reactive water and oxygen on the surface in contact with the anode side gas diffusion layer. Further, the anode separator may have a flow path for a cooling medium for keeping the temperature of the water electrolysis cell constant on the surface opposite to the surface in contact with the anode side gas diffusion layer. The cathode separator may have flow paths for cathode fluids such as hydrogen on the surface in contact with the cathode side gas diffusion layer. Further, the cathode separator may have a flow path for a cooling medium for keeping the temperature of the water electrolysis cell constant on the surface opposite to the surface in contact with the cathode side gas diffusion layer. The separator may be a gas-impermeable conductive member or the like. Examples of the conductive member include dense carbon obtained by compressing resin materials such as thermosetting resins, thermoplastic resins, and resin fibers, carbon materials such as carbon powder and carbon fibers, and press-molded metal (for example, titanium and stainless steel) plates. The shape of the separator may be rectangular, horizontally long hexagon, horizontally long octagon, circular, oblong, or the like.

[0021] In a plan view of the separator, a seal member surrounding the oxygen electrode side supply hole and a seal member surrounding the oxygen electrode side discharge hole are arranged, and the seal members surrounding the respective holes are not arranged for the hydrogen electrode side supply hole, the hydrogen electrode side discharge hole, the inter-cell flow path supply hole, and the inter-cell flow path discharge hole. The seal member may be a conventionally known gasket, resin sheet, or the like.

[0022] The water electrolysis cell may include an electrode portion. The electrode portion has, in this order, an anode side gas diffusion layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, and a cathode side gas diffusion layer, and may have, in this order, an anode side gas diffusion layer, an anode side microporous layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, a cathode side microporous layer, and a cathode side gas diffusion layer as necessary. From the viewpoint of suppressing the occurrence of plastic deformation of the electrolyte membrane due to the generation of differential pressure between the hydrogen electrode and the oxygen electrode, the electrode portion may have at least a cathode side microporous layer among the anode side microporous layer and the cathode side microporous layer.

[0023] The cathode (hydrogen electrode) includes a cathode catalyst layer and a cathode side gas diffusion layer, and may include a cathode side microporous layer between the cathode catalyst layer and the cathode side gas diffusion layer as necessary. The anode (oxygen electrode) includes an anode catalyst layer and an anode side gas diffusion layer, and may include an anode side microporous layer between the anode catalyst layer and the anode side gas diffusion layer as necessary. In the water electrolysis cell, the area of one of the oxygen electrode and the hydrogen electrode may be smaller than the area of the other, and the area of the oxygen electrode may be smaller than the area of the hydrogen electrode. Thereby, the electrode portion of the water electrolysis cell has a stepped structure at the end in the plane direction. Among the oxygen electrode and the hydrogen electrode, the catalyst layer, the microporous layer, and the gas diffusion layer of the electrode with the smaller area may all have an area smaller than that of the electrolyte membrane. Among the oxygen electrode and the hydrogen electrode, as long as the catalyst layer, the microporous layer, and the gas diffusion layer of the electrode with the smaller area have an area smaller than that of the electrolyte membrane, the relative sizes of these areas are not particularly limited. In the water electrolysis cell of the present disclosure, the pressure of the hydrogen electrode in the water electrolysis cell may be made higher than the pressure of the oxygen electrode.

[0024] The cathode catalyst layer and the anode catalyst layer are collectively referred to as the catalyst layer. The catalyst layer may include, for example, a catalyst metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, a carrier having electron conductivity, and the like. As the catalyst metal, for example, iridium (Ir), iridium dioxide (IrO2), ruthenium (Ru), platinum (Pt), and an alloy composed of Pt and other metals (for example, a Pt alloy mixed with cobalt, nickel, etc.) can be used. For the anode catalyst layer, for example, Ir, IrO2, Ru, etc. can be used as the catalyst metal, and for the cathode catalyst layer, for example, Pt, a Pt alloy, etc. can be used as the catalyst metal. As the electrolyte, a fluororesin or the like may be used. As the fluororesin, for example, a Nafion solution or the like can be used. The above catalyst metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalyst metal (catalyst-supporting carrier) and the electrolyte may be mixed. Examples of the carrier for supporting the catalyst metal include carbon materials such as commercially available carbon.

[0025] The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of the solid polymer electrolyte membrane include fluorine-based electrolyte membranes such as thin films of perfluorosulfonic acid containing moisture, and hydrocarbon-based electrolyte membranes. As the electrolyte membrane, for example, a Nafion membrane (manufactured by DuPont) or the like may be used.

[0026] The cathode-side gas diffusion layer and the anode-side gas diffusion layer are collectively referred to as the gas diffusion layer. The gas diffusion layer may be a gas-permeable member, i.e., a conductive member having pores. Examples of the conductive member include carbon porous bodies such as carbon cloth and carbon paper, and metal porous bodies such as metal mesh and foamed metal.

[0027] The anode-side microporous layer and the cathode-side microporous layer are collectively referred to as the microporous layer. The microporous layer may be a mixture of a water-repellent resin such as PTFE and a conductive material such as carbon black. The microporous layer may have pores with a size of 1 to several hundred μm.

[0028] The support frame is disposed on the outer periphery of the electrode portion and between the cathode separator and the anode separator. The support frame may have a skeleton portion, an opening portion, and holes. The skeleton portion is the main part of the support frame that connects to the electrode portion. The opening portion is a holding region of the electrode portion and is a region that penetrates a part of the skeleton portion to accommodate the electrode portion. The opening portion may be disposed at a position where the skeleton portion is disposed around (outer peripheral portion) the electrode portion in the support frame, or may be provided at the center of the support frame. The holes in the support frame allow fluids such as reaction water, oxygen, hydrogen, and a cooling medium to flow in the stacking direction of the water electrolysis cell. The holes in the support frame may be aligned and disposed so as to communicate with the holes in the separator. The support frame may include a frame-shaped core layer and two frame-shaped shell layers provided on both sides of the core layer, i.e., a first shell layer and a second shell layer. The first shell layer and the second shell layer may be provided in a frame shape on both sides of the core layer in the same manner as the core layer.

[0029] The core layer may be a structural member having gas sealing properties and insulation properties, and may be formed of a material whose structure does not change even under the temperature conditions during thermocompression bonding in the manufacturing process of the water electrolysis cell. Specifically, the material of the core layer may be, for example, resins such as polyethylene, polypropylene, PC (polycarbonate), PPS (polyphenylene sulfide), PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PA (polyamide), PI (polyimide), PS (polystyrene), PPE (polyphenylene ether), PEEK (polyether ether ketone), cycloolefin, PES (polyether sulfone), PPSU (polyphenyl sulfone), LCP (liquid crystal polymer), epoxy resin, etc. The material of the core layer may be a rubber material such as EPDM (ethylene propylene diene rubber), fluorine-based rubber, silicon-based rubber, etc. From the viewpoint of ensuring insulation properties, the thickness of the core layer may be 5 μm or more, or 20 μm or more. From the viewpoint of reducing the thickness of the water electrolysis cell, it may be 200 μm or less, or 150 μm or less.

[0030] The first shell layer and the second shell layer may have high adhesiveness to other substances and soften under the temperature conditions during thermocompression bonding in order to adhere the core layer to the anode separator and the cathode separator to ensure sealing properties, and may have properties of lower viscosity and melting point than the core layer. Specifically, the first shell layer and the second shell layer may be thermoplastic resins such as polyester-based and modified olefin-based resins, or may be thermosetting resins which are modified epoxy resins. The resin constituting the first shell layer and the resin constituting the second shell layer may be the same type of resin or different types of resins. By providing shell layers on both sides of the core layer, adhesion by hot pressing between the support frame and the two separators becomes easy. From the viewpoint of ensuring adhesiveness, the thickness of each of the first shell layer and the second shell layer may be 5 μm or more, or 30 μm or more. From the viewpoint of reducing the thickness of the water electrolysis cell, it may be 100 μm or less, or 40 μm or less.

[0031] In the support frame, the first shell layer and the second shell layer may be provided only at portions that adhere to the anode separator and the cathode separator, respectively. The first shell layer provided on one surface of the core layer may adhere to the cathode separator. The second shell layer provided on the other surface of the core layer may adhere to the anode separator. And the support frame may be sandwiched by a pair of separators.

[0032] The water electrolysis cell stack may have manifolds such as an inlet manifold in which each supply hole communicates and an outlet manifold in which each discharge hole communicates. Examples of the inlet manifold include an oxygen electrode inlet manifold, a hydrogen electrode inlet manifold, and a cooling medium inlet manifold. Examples of the outlet manifold include an oxygen electrode outlet manifold, a hydrogen electrode outlet manifold, and a cooling medium outlet manifold. The oxygen electrode inlet manifold and the oxygen electrode outlet manifold are collectively referred to as the oxygen electrode manifold. The hydrogen electrode inlet manifold and the hydrogen electrode outlet manifold are collectively referred to as the hydrogen electrode manifold. The cooling medium inlet manifold and the cooling medium outlet manifold are collectively referred to as the cooling medium manifold.

Explanation of Reference Numerals

[0033] 10 Anode separator 11 Anode-side gas diffusion layer 12 Anode-side microporous layer 13 Anode catalyst layer 14 Electrolyte membrane 15 Cathode catalyst layer 16 Cathode-side microporous layer 17 Cathode-side gas diffusion layer 18 Cathode separator 19 Support frame 20 Oxygen electrode-side supply hole 21 Oxygen electrode-side discharge hole 30 Hydrogen electrode-side supply hole 31 Hydrogen electrode-side discharge hole Inter-cell flow path supply hole 40 Inter-cell flow path discharge hole 41 Outer peripheral seal member 50 Seal member 51 Conventional separator 60 Separator of the present disclosure 70 Water electrolysis cell 100

Claims

1. A water electrolysis cell, wherein the water electrolysis cell includes a separator having grooves serving as flow paths on the front and back surfaces, the separator has, in a plan view, an oxygen electrode side supply hole, an oxygen electrode side discharge hole, a hydrogen electrode side supply hole, a hydrogen electrode side discharge hole, an inter-cell flow path supply hole, and an inter-cell flow path discharge hole at the end portions in the plane direction, in the plan view of the separator, a seal member surrounding the oxygen electrode side supply hole and a seal member surrounding the oxygen electrode side discharge hole are arranged, and no seal member surrounding each hole is arranged at the hydrogen electrode side supply hole, the hydrogen electrode side discharge hole, the inter-cell flow path supply hole, and the inter-cell flow path discharge hole; a water electrolysis cell.

2. The water electrolysis cell according to claim 1, having an electrode part, a support frame having an opening surrounding the electrode part, and a pair of the separators sandwiching the electrode part and the support frame.

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