Water electrolysis cell and water electrolysis cell stack

Abstract

The present disclosure relates to a water electrolysis cell, and a stack of water electrolysis cells stacked with water electrolysis cells. Provided is a water electrolysis cell in which the concentration of hydrogen reaching the oxygen-generating electrode side is reduced to the concentration before the concentration is increased, with a simple configuration. The water electrolysis cell is provided with an electrolyte membrane, a catalyst layer, and a diaphragm through which a fluid flows, and generates hydrogen and oxygen by supplying water and applying a voltage thereto, in which a hydrogen reaction catalyst for promoting a reaction between hydrogen and oxygen is provided at a site where the generated oxygen and the remaining water flow on the surface of the diaphragm on the oxygen generation electrode side.

Description

Technical Field

[0001] The present disclosure relates to a water electrolysis cell and a water electrolysis cell stack in which the water electrolysis cells are stacked. Background Art

[0002] Patent Document 1 discloses a technique in which a mixed gas of hydrogen and oxygen reacts on a fluid passage connecting a water electrolysis device to a hydrogen tank or an oxygen tank and is changed into water vapor, thereby reducing the concentration of gaseous hydrogen or oxygen. The generated water vapor is separated midway.

[0003] Patent Document 1: WO2019 / 008799 Specification

[0004] In the prior art as in Patent Document 1, the reaction device needs to be separately provided outside the water electrolysis device, which hinders the miniaturization of the entire water electrolysis system. In addition, there is also a concern that a mixed gas of hydrogen and oxygen with a high concentration is generated when gas-liquid separation is performed, and large-scale gas concentration management is required. Summary of the Invention

[0005] In view of the above problems, an object of the present disclosure is to provide a water electrolysis cell that can reduce the concentration of hydrogen reaching the oxygen generation electrode side to that before the concentration increase with a simple structure.

[0006] The present application discloses a water electrolysis cell including an electrolyte membrane, a catalyst layer, and a diaphragm through which a fluid flows. Water is supplied and a voltage is applied thereto to generate hydrogen and oxygen. A hydrogen reaction catalyst that promotes the reaction between hydrogen and oxygen is provided at a portion on the surface of the diaphragm on the oxygen generation electrode side where the generated oxygen and the remaining water flow.

[0007] It may also be configured such that a portion where the hydrogen reaction catalyst is disposed has a structure that generates turbulence in the remaining water.

[0008] The structure that generates turbulence can be a groove and / or embossing provided in a region leading to a discharge hole for the remaining water, that is, a lead-out region.

[0009] Alternatively, it may be configured such that the hydrogen reaction catalyst is provided in a flow path for discharging the remaining water on the downstream side of the region where water electrolysis is performed on the surface of the diaphragm.

[0010] It may also be configured such that the hydrogen reaction catalyst is disposed on a surface of the diaphragm facing a frame that separates the oxygen generation electrode and the hydrogen generation electrode.

[0011] It may also be configured such that the hydrogen reaction catalyst is disposed on a surface of the diaphragm facing an adjacent water electrolysis cell.

[0012] It may also be configured such that the hydrogen reaction catalyst is disposed on a surface of a frame that separates the oxygen generation electrode and the hydrogen generation electrode.

[0013] According to the present disclosure, hydrogen and oxygen react in the water electrolysis cell, so there is no need to provide a large-scale device for reducing the concentration of hydrogen on the downstream side of the oxygen generation electrode side path of the system, enabling miniaturization of the system. In addition, hydrogen concentration management can also be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a top view of the water electrolysis cell 10.

[0015] Figure 2 It is a schematic diagram for explaining the layer structure in the water electrolysis region 10a of the water electrolysis cell 10.

[0016] Figure 3 It is a schematic diagram for explaining the layer structure in the oxygen electrode outlet side distribution region 10d and the oxygen electrode outlet region 10e of the water electrolysis cell 10.

[0017] Figure 4 It is a diagram for explaining an example of the shape of the groove 14h as a structure for generating turbulence.

[0018] Figure 5 It is a diagram for explaining an example of the shape of the groove 14h as a structure for generating turbulence.

[0019] Figure 6 It is a diagram for explaining an example of the shape of the groove 14h as a structure for generating turbulence.

[0020] Figure 7 It is a diagram for explaining the shape of the frame 18.

[0021] Figure 8 It is a diagram for explaining another form of the flow of the fluid on the oxygen generation electrode side.

[0022] Figure 9 It is a schematic diagram for explaining the structure of the water electrolysis cell stack 30.

[0023] Figure 10 It is a diagram for explaining the stacked structure of the water electrolysis cells 10 in the water electrolysis cell stack 30.

[0024] Figure 11 It is a schematic diagram for explaining another form of the layer structure in the oxygen electrode outlet side distribution region 10d and the oxygen electrode outlet region 10e in the stacked structure of the water electrolysis cell 10.

[0025] REFERENCE MARK DESCRIPTION

[0026] 10…Water electrolysis cell; 10a…Water electrolysis region; 10b…Oxygen electrode inlet region; 10c…Oxygen electrode inlet side distribution region; 10d…Oxygen electrode outlet side distribution region; 10e…Oxygen electrode outlet region; 11…Solid polymer electrolyte membrane (electrolyte membrane); 12…Anode catalyst layer (catalyst layer); 13…Anode gas diffusion layer (oxygen generation electrode gas diffusion layer); 14…Anode separator (oxygen generation electrode separator); 14a…Supply flow path; 14d…Oxygen electrode side inlet manifold (oxygen electrode inlet hole); 14e…Oxygen electrode side outlet manifold (oxygen electrode outlet hole); 14f…Hydrogen electrode side outlet manifold (hydrogen electrode outlet hole); 14g…Constriction portion (structure for generating turbulence); 14h…Groove (structure for generating turbulence); 14j…Hole; 15…Cathode catalyst layer (catalyst layer); 16…Cathode gas diffusion layer (hydrogen generation electrode gas diffusion layer); 17…Cathode separator (hydrogen generation electrode separator); 18…Frame; 20…Hydrogen reaction portion (portion having a hydrogen reaction catalyst); 30…Water electrolysis cell stack. Detailed Description of the Embodiment

[0027] 1. Water electrolysis cell

[0028] In Figure 1 FIG. shows a diagram for explaining the structure of a water electrolysis cell 10 according to an embodiment. The water electrolysis cell 10 is a unit element for decomposing pure water into hydrogen and oxygen, and a water electrolysis cell stack is formed by laminating a plurality of such water decomposition cells 10. Figure 1 is a top view of the water electrolysis cell 10. In Figure 1 FIG., in order to explain the internal structure of the water electrolysis cell 10, a part of the internal structure (particularly the oxygen generation electrode side) is shown by a dashed line.

[0029] The water electrolysis in the water electrolysis cell 10 is a well-known technique and will be briefly described later.

[0030] Pure water flows into the oxygen electrode inlet region 10b from the oxygen electrode inlet hole (oxygen electrode side inlet manifold) 14d. Thereafter, the pure water reaches the water electrolysis region 10a after the uniformity of the distribution is improved in the oxygen electrode inlet side distribution region 10c, and water electrolysis is performed here.

[0031] In the water electrolysis region 10a, a part of the pure water is decomposed into oxygen and hydrogen by the water electrolysis membrane electrode assembly described later, and is discharged through their respective flow paths. The generated oxygen and the remaining pure water are collected by the oxygen electrode outlet flow path 10e via the oxygen electrode outlet side distribution region 10d, and are discharged from the oxygen electrode outlet hole (oxygen electrode side outlet manifold) 14e.

[0032] On the other hand, the generated hydrogen moves to the electrode (hydrogen generation electrode) on the opposite side of the electrode (oxygen generation electrode) where pure water flows across the water electrolysis membrane electrode assembly, and is discharged through another flow path (not shown) from the hydrogen electrode outlet hole (hydrogen electrode side outlet manifold) 14f. Both the oxygen generation electrode and the hydrogen generation electrode are provided in the water electrolysis cell 10, but outside the water electrolysis region 10a, they are separated by a sealing member (not shown) so that the generated hydrogen and oxygen do not mix, forming separate flow paths for each.

[0033] Hereinafter, the structure of the water electrolysis cell 10 will be described. Figure 2 is Figure 1 a part of the A-A cross-section, and is a diagram for explaining the layer structure in the water electrolysis region 10a where water electrolysis is performed in the water electrolysis cell 10. Figure 3 is Figure 1 the B-B cross-section, and is a diagram showing the layer structure of a part of the oxygen electrode outlet hole (oxygen electrode side outlet manifold) 14e, the oxygen electrode outlet region 10e, the oxygen electrode outlet side distribution region 10d, and a part of the water electrolysis region 10a.

[0034] The water electrolysis cell 10 is composed of multiple layers. With the solid polymer electrolyte membrane 11 interposed therebetween, one side is the oxygen generation electrode (anode), and the other side is the hydrogen generation electrode (cathode).

[0035] In the water electrolysis region 10a, as Figure 2 shown, on the anode side starting from the solid polymer electrolyte membrane 11, an anode catalyst layer 12, an anode gas diffusion layer 13, and an anode separator 14 are laminated in sequence. On the other hand, on the cathode side starting from the solid polymer electrolyte membrane 11, a cathode catalyst layer 15, a cathode gas diffusion layer 16, and a cathode separator 17 are provided in sequence. Here, the water electrolysis membrane electrode assembly refers to a laminate of the solid polymer electrolyte membrane 11, the anode catalyst layer 12 disposed on the anode side of the solid polymer electrolyte membrane 11, and the cathode catalyst layer 15 disposed on the cathode side of the solid polymer electrolyte membrane 11. The thickness of the water electrolysis membrane electrode assembly is typically about 0.4 mm, and the thickness of the water electrolysis cell 10 in the water electrolysis region 10a is typically about 1.3 mm.

[0036] On both end sides of the water electrolysis region 10a of the water electrolysis cell 10, as Figure 3 shown, a frame 18 and a hydrogen reaction part 20 are provided.

[0037] First, the morphology of each layer will be described, and then the layer structure in each region will be described.

[0038] 1.1. Morphology of Each Layer

[0039] Each layer provided in the water electrolysis cell 10 has the following morphology, for example. However, the water electrolysis cell of the present disclosure is not limited to this morphology.

[0040] [Solid polymer electrolyte membrane]

[0041] The solid polymer electrolyte membrane 11 is a form of electrolyte membrane having proton conductivity. In the present embodiment, the material (electrolyte) constituting the solid polymer electrolyte membrane 11 is a solid polymer material, and examples thereof include proton-conductive ion exchange membranes formed of fluororesins, hydrocarbon resin materials, etc. It exhibits good proton conductivity (electric conductivity) in a wet state. More specifically, a membrane formed of perfluorosulfonic acid (Nafion, registered trademark), which is a perfluorinated electrolyte, can be cited.

[0042] The thickness of the solid polymer electrolyte membrane 11 is not particularly limited, and is 200 μm or less, preferably 100 μm or less, and more preferably 30 μm or less.

[0043] [Anode catalyst layer]

[0044] The anode catalyst layer (oxygen electrode catalyst layer) 12 is a catalyst layer having a catalyst containing at least one or more noble metal catalysts such as Pt, Ru, Ir and their oxides. As the catalyst, more specifically, Pt, iridium oxide, ruthenium oxide, iridium ruthenium oxide, or a mixture thereof can be cited.

[0045] As the iridium oxide, iridium oxide (IrO2, IrO3), iridium tin oxide, iridium zirconium oxide, etc. can be cited.

[0046] As the ruthenium oxide, ruthenium oxide (RuO2, Ru2O3), ruthenium tantalum oxide, ruthenium zirconium oxide, ruthenium titanium oxide, ruthenium titanium cerium oxide, etc. can be cited.

[0047] As the iridium ruthenium oxide, iridium ruthenium cobalt oxide, iridium ruthenium tin oxide, iridium ruthenium iron oxide, iridium ruthenium nickel oxide, etc. can be cited.

[0048] Here, the anode catalyst layer 12 may also contain an ionomer. By containing the ionomer, in addition to improving the coatability, the permeation of water supplied during water decomposition can be smoothly carried out due to its hydrophilicity. As the ionomer to be contained, an ionomer containing a perfluorinated electrolyte used as an electrolyte for the solid polymer electrolyte membrane can be cited.

[0049] [Anode gas diffusion layer]

[0050] The anode gas diffusion layer 13 is a gas diffusion layer disposed on the anode side, and a known gas diffusion layer can be used, but it is composed of a member having air permeability and conductivity. Specifically, a porous conductive member composed of a sintered body of metal fibers (e.g., titanium fibers) or metal particles (titanium particles) can be cited.

[0051] [Anode membrane]

[0052] The anode membrane 14 is a component (membrane) having a flow path (water supply flow path) 14a through which pure water supplied to the anode gas diffusion layer 13 and decomposed oxygen flow. In the present embodiment, the anode membrane 14 is a component in which a plate-like component is formed in a wave shape with repeated concavities and convexities in the water electrolysis region 10a, and by disposing the concave portion 14c in contact with the anode gas diffusion layer 13, a water supply flow path 14a is formed between the anode gas diffusion layer 13 and the convex portion 14b.

[0053] The anode membrane 14 can be made, for example, by stamping a titanium thin film, and its plate thickness is typically 0.1 mm to 0.2 mm, and the height of the concavities and convexities is typically about 0.5 mm.

[0054] In addition, as Figure 1 described above, an inlet manifold 14d for pure water, that is, an oxygen electrode side inlet manifold, an outlet manifold 14e for the generated oxygen and remaining water, that is, an oxygen electrode side outlet manifold, and an outlet manifold 14f for the generated hydrogen and water accompanying it, that is, a hydrogen electrode side outlet manifold, are provided in the anode membrane 14.

[0055] Moreover, as Figure 3 shown, in the anode membrane 14 of the present embodiment, a constriction portion 14g is provided in the oxygen electrode lead-out region 10e so as to protrude toward the cathode membrane 17 side. The constriction portion 14g functions as one of the structures for generating turbulence, and thereby, as will be described later, the flow of the fluid can be disturbed on the surface of the anode membrane 14 to promote the hydrogen reaction in the hydrogen reaction portion 20.

[0056] In addition, in the present embodiment, it may be configured such that a groove 14h is provided on the surface on the cathode membrane 17 side in the oxygen electrode lead-out side distribution region 10d and / or the oxygen electrode lead-out region 10e continuous therewith in the anode membrane 14. The groove 14h also functions as one of the structures for generating turbulence, and thereby, as will be described later, the flow of the fluid can be disturbed on the surface of the anode membrane 14 to promote the hydrogen reaction in the hydrogen reaction portion 20.

[0057] In Figures 4 - 6 a morphological example of the groove 14h is schematically shown. In addition, Figures 4 - 6 the direction of the straight arrow shown is the direction indicated by H in Figure 1 .

[0058] Figure 4 The example of

[0059] Figure 5 is a shape in which the groove width changes in the extending direction of the groove 14h.

[0060] Figure 6 An example is an example where the grooves 14h adjacent in the extending direction of the groove 14h merge (grooves that separate midway can also be formed).

[0061] In addition, as a morphological example of the structure for generating turbulence, it can also be unevenness such as a constant groove width and linear, wavy, or embossed shapes in the extending direction of the groove.

[0062] In addition, a conduction layer can be provided at the positions corresponding to the water electrolysis region 10a on the front and back sides of the anode diaphragm 14 to reduce the electrical contact resistance. The material constituting the conduction layer only needs to have conductivity, and for example, platinum can be cited.

[0063] [Cathode catalyst layer]

[0064] The cathode catalyst layer 15 is a catalyst layer containing a catalyst. The catalyst contained in the cathode catalyst layer 15 can use known catalysts, and for example, platinum, platinum-coated titanium, platinum-supported carbon, palladium-supported carbon, cobalt glyoxime, nickel glyoxime, etc. can be cited.

[0065] Here, the cathode catalyst layer 15 can also contain an ionomer. By containing an ionomer, improved coatability can be achieved. As the ionomer contained, an ionomer composed of a perfluorinated electrolyte used as an electrolyte for a solid polymer electrolyte membrane can be cited.

[0066] [Cathode gas diffusion layer]

[0067] The cathode gas diffusion layer 16 is a gas diffusion layer disposed on the cathode side and can use a known gas diffusion layer, but is composed of a component having air permeability and conductivity. Specifically, porous components such as carbon cloth and carbon paper can be cited.

[0068] [Cathode diaphragm]

[0069] The cathode diaphragm 17 is a component having a flow path 17a through which hydrogen and water (accompanying water) accompanying the reduction of hydrogen ions reach when passing through the solid polymer electrolyte membrane 11. In the present embodiment, the cathode diaphragm 17 is a component in which a plate-like component is formed into a wave shape and the unevenness is repeated in the water electrolysis region 10a. By disposing the concave portion 17c in contact with the cathode gas diffusion layer 16, a flow path 17a for hydrogen discharge is formed between the cathode gas diffusion layer 16 and the convex portion 17b.

[0070] The cathode diaphragm 17 can be formed, for example, by stamping a titanium thin film, and its plate thickness is typically 0.1 mm to 0.2 mm, and the height of the unevenness is typically about 0.5 mm.

[0071] In addition, in the cathode diaphragm 17, asFigure 1 As described above, an oxygen electrode side inlet manifold (not shown) that overlaps with the above-described oxygen electrode side inlet manifold 14d, an oxygen electrode side outlet manifold (not shown) that overlaps with the above-described oxygen electrode side outlet manifold 14e, and a hydrogen electrode side outlet manifold (not shown) that overlaps with the above-described hydrogen electrode side outlet manifold 14f are provided.

[0072] A conduction layer may also be provided at positions corresponding to the water electrolysis region 10a on both the front and back sides of the cathode diaphragm 17 in order to reduce the electrical contact resistance. The material constituting the conduction layer only needs to have conductivity, and for example, platinum can be cited.

[0073] [Frame]

[0074] The frame 18 is disposed between the anode diaphragm 14 and the cathode diaphragm 17 at the outer peripheral portion of the water electrolysis cell 10, seals its inner side, and functions as a sealing member that seals in a manner that isolates the oxygen generation electrode side from the hydrogen generation electrode side.

[0075] Therefore, the frame 18 surrounds the water electrolysis region 10a, the oxygen electrode introduction region 10b, the oxygen electrode introduction side dispersion region 10c, the oxygen electrode export side dispersion region 10d, the oxygen electrode export region 10e, etc., and is disposed in a manner sandwiched between the anode diaphragm 14 and the cathode diaphragm 17.

[0076] For example, in Figure 3 In the cross-section, in order for the generated oxygen and residual water to flow from the water supply flow path 14a of the anode diaphragm 14 through the oxygen electrode export side distribution region 10d and the oxygen electrode export region 10e to the oxygen electrode side outlet manifold 14e, the frame 18 is unsealed in this part. On the other hand, in Figure 3 In the cross-section, it is sealed in a manner that cuts off the flow of hydrogen from the flow path 17a of the cathode diaphragm 17 to the oxygen electrode side inlet manifold 14e. In this way, the frame 18 adjusts the contact (sealing) with the anode diaphragm 14 and the cathode diaphragm 17 so that the flow of the fluid becomes appropriate.

[0077] The frame 18 is formed of a thermoplastic resin material having electrical insulation and airtightness and a relatively high melting point. As such a material, crystalline polymers can be cited, and more specifically, engineering plastics. As engineering plastics, for example, polyethylene naphthalate resin (PEN) and polyethylene terephthalate resin (PET) can be cited.

[0078] The thickness of the frame is not particularly limited, but is preferably 0.05 mm or more and 0.25 mm or less.

[0079] In the present embodiment, a plurality of holes 18a may also be provided at the position of the frame 18 that becomes the oxygen electrode export region 10e. In Figure 7 In, a diagram for explanation is shown. InFigure 7 In it, a view of the same perspective is shown on the upper side of the paper surface, and a plan view of a part of the frame 18 is shown on the lower side of the paper surface. Figure 3 In this way, the part leading to the oxygen electrode outlet manifold 14e at the position that becomes the oxygen electrode lead-out region 10d in the frame 18 is not a simple single cut, but is composed of a plurality of holes 18a. By being the plurality of holes 18a, it functions as a structure for generating turbulence, and as will be described later, it can disturb the fluid flow on the surface of the anode diaphragm 14 to promote the hydrogen reaction in the hydrogen reaction part 20.

[0080] Thus, the part leading to the oxygen electrode outlet manifold 14e at the position that becomes the oxygen electrode lead-out region 10d in the frame 18 is not a simple single cut, but is composed of a plurality of holes 18a. By being the plurality of holes 18a, it functions as a structure for generating turbulence, and as will be described later, it can disturb the fluid flow on the surface of the anode diaphragm 14 to promote the hydrogen reaction in the hydrogen reaction part 20.

[0081] [Hydrogen reaction part]

[0082] The hydrogen reaction part 20 is a part where hydrogen that reaches here reacts with oxygen to be converted into water. Therefore, in the present embodiment, a hydrogen reaction catalyst is arranged in the hydrogen reaction part 20, thereby promoting this reaction. The hydrogen reaction catalyst is not particularly limited, but for example, platinum can be cited. In the case of using platinum, from the viewpoint of reducing the usage amount of precious metals, the film thickness is preferably 100 nm or less, and more preferably 30 nm or less. The method of forming the platinum film is not particularly limited, but for example, a so-called surface treatment method can be used. As the surface treatment method, specifically, ion plating, sputtering, electroplating, etc. can be cited.

[0083] The hydrogen reaction part may be arranged to have a certain film thickness and cover a specified entire range, but it is not limited thereto, and it can also be scattered in an island shape or alternately arranged in a striped shape.

[0084] The part where the hydrogen reaction part 20 is provided is an area where the generated oxygen and the remaining water flow. Therefore, specifically, the hydrogen reaction catalyst can be provided on the inner surface of the diaphragm on the downstream side of the water electrolysis area in the flow path for discharging the remaining water. More specifically, as Figure 3 shown, it can be cited the inner surface (the surface on the side where the water electrolysis membrane electrode assembly is arranged) of the anode diaphragm 14, and the inner surface (the surface facing the frame 18) of the flow path that forms a flow path for supplying oxygen and the remaining water in the oxygen electrode lead-out side distribution area 10d and / or the oxygen electrode lead-out area 10e. In addition, on this basis, the hydrogen reaction part can also be further formed on the surface of the frame 18 (the surface on the oxygen electrode side), or instead, the hydrogen reaction part can be formed on the surface of the frame 18 (the surface on the oxygen electrode side).

[0085] Thereby, the hydrogen mixed in the generated oxygen and the remaining water (permeating from the hydrogen production electrode side) can be combined with oxygen and react on the inner surface of the flow path formed by the anode diaphragm to become water.

[0086] In addition, when the remaining water discharged from the water electrolysis cell 10 is treated and then supplied to the water electrolysis cell 10 again, hydrogen may be contained in the supplied water. Therefore, a hydrogen reaction part may also be provided in the flow paths of the oxygen electrode introduction region 10c and the oxygen electrode introduction side distribution region 10c connected thereto.

[0087] 1.2. Layer structure of the water electrolysis region

[0088] As Figure 2 shown, for the layer structure of the water electrolysis region 10a, an anode catalyst layer 12, an anode gas diffusion layer 13, and an anode separator 14 are laminated in sequence from the side of the solid polymer electrolyte membrane 11. On the other hand, the cathode includes a cathode catalyst layer 15, a cathode gas diffusion layer 16, and a cathode separator 17 in sequence from the side of the solid polymer electrolyte membrane 11.

[0089] The anode separator 14 has a flow path (water supply flow path) 14a through which pure water supplied to the anode gas diffusion layer 13 and decomposed oxygen flow. In the present embodiment, the anode separator 14 forms a plate-like member into a wave shape and repeats unevenness in the water electrolysis region 10a, and by disposing the concave portion 14c in contact with the anode gas diffusion layer 13, a water supply flow path 14a is formed between the anode gas diffusion layer 13 and the convex portion 14b.

[0090] The cathode separator 17 has a flow path 17a through which hydrogen generated by reducing hydrogen ions and water (accompanying water) accompanying the permeation of hydrogen ions through the solid polymer electrolyte membrane 11 reach. In the present embodiment, the cathode separator 17 forms a plate-like member into a wave shape and repeats unevenness in the water electrolysis region 10a, and by disposing the concave portion 17c in contact with the cathode gas diffusion layer 16, a flow path 17a for hydrogen discharge is formed between the cathode gas diffusion layer 16 and the convex portion 17b.

[0091] 1.3. Layer structure of the oxygen electrode outlet side distribution region and the oxygen electrode outlet region

[0092] The oxygen electrode outlet side distribution region 10d and the oxygen electrode outlet region 10e are regions through which oxygen and remaining water generated in the water electrolysis region 10a pass before being discharged to the oxygen electrode side outlet manifold 14e.

[0093] In the oxygen electrode outlet side distribution region 10d, according to Figure 3It can be seen that the end faces of the solid polymer electrolyte membrane 11, the anode catalyst layer 12, the anode gas diffusion layer 13, the cathode catalyst layer 15, and the cathode gas diffusion layer 16 are formed. Here, the end face of the anode gas diffusion layer 13 is formed at a slightly receded position compared to the other end faces. Moreover, the frame 18 is configured in a manner stacked with the anode catalyst layer 12 and extending from the end face of the anode gas diffusion layer 13. The frame 18 is configured to reach the oxygen electrode lead-out area 10e and extend to the oxygen electrode outlet manifold 14e. In addition, in the oxygen electrode lead-out side distribution area 10d, the cathode diaphragm 17 is bent in the thickness direction (the stacking direction of each layer) to contact the surface of the frame 18, thereby sealing the hydrogen generating electrode side.

[0094] In the oxygen electrode lead-out region 10 e , the anode separator 14 is bent so as to approach the frame 18 , forming a constricted portion 14 g , thereby narrowing the flow path in the thickness direction.

[0095] In this embodiment, as described above, the hydrogen reaction unit 20 is arranged on the surface of the anode separator 14 on the frame 18 side, on the surface forming the flow path, in the oxygen electrode lead-out side distribution region 10 d and the oxygen electrode lead-out region 10 e .

[0096] 1.4. Effects, etc.

[0097] The water electrolysis cell 10 according to the present disclosure functions as follows, for example.

[0098] When pure water is supplied from the oxygen electrode side inlet manifold 14d, the pure water reaches the water electrolysis area 10a via the oxygen electrode introduction area 10b and the oxygen electrode introduction side distribution area 10c. In the water electrolysis area 10a, by passing electricity between the anode and the cathode, the pure water (H2O) supplied from the water supply flow path 14a to the anode (oxygen generating electrode) is decomposed into oxygen, electrons and protons (H + ). At this time, the protons pass through the solid polymer electrolyte membrane 11 and move toward the cathode catalyst layer 15. On the other hand, the electrons separated in the anode catalyst layer 12 pass through the external circuit and reach the cathode catalyst layer 15. Then, in the cathode catalyst layer 15, the protons accept the electrons to generate hydrogen (H2), which then reaches the cathode gas diffusion layer 16. In addition, in the cathode gas diffusion layer 16, water is present along with the generated hydrogen.

[0099] The hydrogen gas and the accompanying water present in the cathode gas diffusion layer 16 reach the cathode separator 17 , flow through the flow path 17 a , and are discharged from the hydrogen electrode side outlet manifold 14 f (hydrogen electrode outlet port).

[0100] On the other hand, the oxygen generated in the anode catalyst layer 12 and the remaining unused water return to the anode diaphragm 14, pass through the hydrogen supply flow path 14a, and are discharged from the oxygen electrode outlet manifold 14e through the flow paths in the oxygen electrode outlet side distribution region 10d and the oxygen electrode outlet region 10e.

[0101] Here, sometimes hydrogen permeating from the hydrogen generation electrode side is mixed into the remaining water discharged from the hydrogen supply flow path 14a. In the water electrolysis cell 10 of the present disclosure, as described above, a hydrogen reaction part 20 is provided on the inner surface of the flow paths in the oxygen electrode outlet side distribution region 10d and the oxygen electrode outlet region 10e, and the mixed hydrogen and oxygen can react here to become water. Thereby, the amount of hydrogen contained in the remaining water collected on the downstream side can be reduced, and equipment for separately treating hydrogen is not required, or its scale can be reduced. In addition, the management of the gas to be treated also becomes easy.

[0102] As in the above-described embodiment, by providing a structure that generates turbulence such as the constriction part 14g, the groove 14h, and the holes 18a of the frame 18, the flow of the flowing remaining water can be easily disturbed, and the mixed hydrogen and the generated oxygen can reach the hydrogen reaction part 20 and be efficiently converted into water.

[0103] In addition, in the above-described water electrolysis cell 10, basically the supplied pure water flows in one direction (from right to left in the drawing) in the water electrolysis region 10a, but instead, it may have the following structure, that is, as indicated by the straight arrows in Figure 8 a partition or the like is provided, and the pure water flows in a manner that folds back at the distribution regions 10c and 10d provided at both ends of the water electrolysis region 10a.

[0104] 2. Water electrolysis cell stack

[0105] 2.1. Basic structure of the water electrolysis cell stack

[0106] The water electrolysis cell stack 30 is a component formed by stacking a plurality (about 50 to 400) of the above-described water electrolysis cells 10, and hydrogen and oxygen are generated by applying electricity to the plurality of water electrolysis cells 10. The schematic structure thereof is shown in Figure 9 . The water electrolysis cell stack 30 includes a cell stack case 31, end plates 32, a plurality of water electrolysis cells 10, and a biasing member 33.

[0107] The cell stack case 31 is a housing that houses the plurality of stacked water electrolysis cells 10 and the biasing member 33 inside. In the present embodiment, the cell stack case 31 is a quadrilateral cylindrical shape, open at one end and closed at the other end, and a plate-like piece extends along the side of the opening to the side opposite to the opening to form a flange 31a.

[0108] The end plate 32 is a plate-shaped component that closes the opening of the cell stack box 31. The end plate 32 is fixed to the cell stack box 31 in such a manner that the overlapping portion with the flange 31a of the cell stack box 31 is covered by bolts, nuts, etc.

[0109] The water electrolysis cell 10 is as described above. A plurality of such water electrolysis cells 10 are stacked. Here, in the present embodiment, according to Figure 9 it is known that the water electrolysis cells 10 are configured to be stacked in the horizontal direction. In each of the water electrolysis cells 10, as Figure 1 shown, the direction in which the water supply flow paths 14a are arranged and the direction in which the flow paths 17a are arranged are in the vertical direction.

[0110] The biasing member 33 is housed inside the cell stack box 31 and applies a pressing force to the stack of water electrolysis cells 10 in the stacking direction thereof. As the biasing member, for example, a disc spring or the like can be cited.

[0111] 2.2. Stacking structure of water electrolysis cells

[0112] As described above, in the water electrolysis cell stack 30, a plurality of water electrolysis cells 10 are stacked to form. In Figure 10 the figure, three of the stacked water electrolysis cells 10 are taken out and a partial cross-section (a partial cross-section of the water electrolysis region 10a) is shown.

[0113] According to Figure 10 it can be seen that when the water electrolysis cells 10 are stacked, in adjacent water electrolysis cells 10, the cathode diaphragm 17 of one water electrolysis cell 10 overlaps with the anode diaphragm 14 of another water electrolysis cell 10. More specifically, the convex portion 17b of the cathode diaphragm 17 of one water electrolysis cell 10 contacts and overlaps with the convex portion 14b of the anode diaphragm 14 of another water electrolysis cell 10.

[0114] As described above, in the present embodiment, in each of the water electrolysis cells 10, hydrogen and oxygen react to be converted into water. Therefore, even in the water electrolysis cell stack in which many water electrolysis cells 10 are stacked, the above-described effect is achieved, and the more the stacked water electrolysis cells 10 are, the more remarkable the effect is.

[0115] 2.3. Another exemplary form

[0116] In Figure 11 the figure shows a diagram for explaining another exemplary form. In Figure 11 the figure, in the water electrolysis cell stack (i.e., the state in which a plurality of water electrolysis cells 10 are stacked), a portion at the same viewing angle as Figure 3 is shown. In Figure 11 the figure, one water electrolysis cell 10 and a part of one water electrolysis cell 10 stacked therewith are shown.

[0117] In the present embodiment, it is configured such that in the oxygen electrode lead-out region 10e, a sealing material 40 is disposed between the anode diaphragm 14 and the frame 18, and there is no passage from here to the oxygen electrode side outlet manifold 14e. In the present embodiment, instead, a flow path is configured in the following manner, that is, a hole 14j is provided in the oxygen electrode lead-out region 10e of the anode diaphragm 14, a flow path is formed between the anode diaphragm 14 and the cathode diaphragm 17 of the adjacent water electrolysis cell 10, and the flow path leads to the oxygen electrode side outlet manifold 14e.

[0118] As a result, the generated oxygen and the remaining water are bent midway as indicated by the straight arrows, so their flow is disturbed. Therefore, as Figure 11 shown, by providing the hydrogen reaction portion 20 on the inner surface (the surface facing the adjacent water electrolysis cell) of the flow path formed by the anode diaphragm 14 and the cathode diaphragm 17 of the adjacent water electrolysis cell 10, the mixed hydrogen can efficiently react with oxygen. Through such an embodiment, the above-described effects are also achieved.

Claims

1. A water electrolysis cell includes an electrolyte membrane, a catalyst layer, and a diaphragm through which a fluid flows, and generates hydrogen and oxygen by supplying water and applying an external voltage. Among them, a hydrogen reaction catalyst that promotes the reaction between hydrogen and oxygen is provided at a portion on the surface of the diaphragm on the oxygen generation electrode side where the generated oxygen and the remaining water flow.

2. The water electrolysis cell according to claim 1, wherein a structure that generates turbulence in the remaining water is provided at the portion where the hydrogen reaction catalyst is disposed.

3. The water electrolysis cell according to claim 2, wherein the structure that generates the turbulence is a groove and / or embossing provided in a region leading to a discharge hole for the remaining water, that is, a lead-out region.

4. The water electrolysis cell according to claim 1, wherein the hydrogen reaction catalyst is provided in a flow path for discharging the remaining water on the downstream side of the water electrolysis region on the surface of the diaphragm.

5. The water electrolysis cell according to claim 4, wherein the hydrogen reaction catalyst is disposed on the surface of the diaphragm facing a frame that separates the oxygen generation electrode and the hydrogen generation electrode.

6. The water electrolysis cell according to claim 4, wherein the hydrogen reaction catalyst is disposed on the surface of the diaphragm facing an adjacent water electrolysis cell.

7. The water electrolysis cell according to claim 4, wherein the hydrogen reaction catalyst is disposed on the surface of a frame that separates the oxygen generation electrode and the hydrogen generation electrode.

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