Water electrolysis cell and water electrolysis stack

Abstract

To provide a water electrolysis cell of a simple configuration capable of reducing the concentration of hydrogen reaching an oxygen-generating electrode before the concentration increases.SOLUTION: A water electrolysis cell comprising an electrolyte membrane, a catalyst layer, and a separator allowing a fluid to flow therethrough, to generate hydrogen and oxygen by supplying water and applying a voltage thereto, is provided with a hydrogen reaction catalyst promoting the reaction of hydrogen and oxygen at a portion of the separator surface on an oxygen-generating electrode side, through which the generated oxygen and remaining water flow.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Patent Document 1 discloses that a mixed gas of hydrogen and oxygen is reacted with each other in a fluid passage connecting a water electrolysis device to a hydrogen tank or an oxygen tank to convert it into water vapor, thereby reducing the concentration of the gaseous hydrogen or oxygen. The generated water vapor is separated along the way. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2019 / 008799 specification Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional technologies such as those described in Patent Document 1 require a separate reactor outside the water electrolysis device, which hinders downsizing of the entire water electrolysis system. In addition, there is a risk that a highly concentrated mixed gas of hydrogen and oxygen may be generated when gas and liquid are separated, requiring extensive management of the gas concentration.

[0005] In view of the above problems, an object of the present disclosure is to provide a water electrolysis cell with a simple configuration that reduces the concentration of hydrogen that has reached the oxygen evolving electrode side before the concentration increases. [Means for solving the problem]

[0006] The present application discloses a water electrolysis cell that includes an electrolyte membrane, a catalyst layer, and a separator through which a fluid flows, and that generates hydrogen and oxygen by supplying water and applying a voltage, and that has a hydrogen reaction catalyst that promotes the reaction between hydrogen and oxygen provided in a portion of the surface of the separator on the oxygen generating electrode side through which the generated oxygen and remaining water flow.

[0007] The area where the hydrogen reaction catalyst is disposed may be provided with a structure for generating turbulence in the remaining water.

[0008] The turbulence generating structures can be grooves and / or embossments in the outlet area, which is the area leading to the drainage holes for the remaining water. [Effects of the Invention]

[0009] According to the present disclosure, hydrogen gas that has permeated to the oxygen evolving electrode side in the water electrolysis cell is reacted with oxygen, eliminating the need to provide a large-scale device for reducing the concentration of hydrogen gas downstream of the oxygen evolving electrode side path in the system, thereby enabling the system to be downsized and facilitating hydrogen concentration management. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view of a water electrolysis cell 10. [Figure 2] FIG. 2 is a conceptual diagram illustrating the layer structure in the water electrolysis region 10a of the water electrolysis cell 10. [Figure 3] FIG. 3 is a conceptual diagram illustrating 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. As shown in FIG. [Figure 4] 10A and 10B are diagrams illustrating examples of the shape of a groove 14h that is a structure for generating turbulent flow. [Figure 5] 10A and 10B are diagrams illustrating examples of the shape of a groove 14h that is a structure for generating turbulent flow. [Figure 6] 10A and 10B are diagrams illustrating examples of the shape of a groove 14h that is a structure for generating turbulent flow. [Figure 7] 2A to 2C are diagrams illustrating the configuration of a frame 18. FIG. [Figure 8] FIG. 10 is a diagram illustrating another aspect of the fluid flow on the oxygen evolution electrode side. [Figure 9] FIG. 9 is a conceptual diagram illustrating the structure of the water electrolysis stack 30. [Figure 10]FIG. 10 is a diagram illustrating the stack structure of the water electrolysis cells 10 in the water electrolysis stack 30. [Figure 11] FIG. 11 is a conceptual diagram illustrating another type of layer configuration in the oxygen electrode lead-out side distribution region 10d and the oxygen electrode lead-out region 10e in the laminated structure of the water electrolysis cell 10. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1.Water electrolysis cell Figure 1 shows a diagram illustrating the structure of a water electrolysis cell 10 according to one embodiment. The water electrolysis cell 10 is a unit element for decomposing pure water into hydrogen and oxygen, and a plurality of such water splitting cells 10 are stacked to form a water electrolysis stack. Figure 1 is a plan view of the water electrolysis cell 10. In Figure 1, part of the internal structure of the water electrolysis cell 10 (particularly the oxygen evolving electrode side) is indicated by dotted lines to illustrate the internal structure.

[0012] The water electrolysis in the water electrolysis cell 10 is well known, but the outline thereof is as follows. Pure water flows into the oxygen electrode introduction region 10b through the oxygen electrode introduction hole (oxygen electrode side inlet manifold) 14d. The pure water is then distributed more uniformly in the oxygen electrode introduction side distribution region 10c, and reaches the water electrolysis region 10a, where water electrolysis takes place. In the water electrolysis region 10a, a portion of the pure water is decomposed into oxygen and hydrogen by a water electrolysis membrane electrode assembly (described later), and the decomposed oxygen and the remaining pure water are discharged through the respective flow paths. The generated oxygen and the remaining pure water pass through the oxygen electrode outlet-side distribution region 10d, are collected by the oxygen electrode outlet flow path 10e, and are discharged from the oxygen electrode outlet hole (oxygen electrode-side outlet manifold) 14e. Meanwhile, the generated hydrogen moves to the electrode (hydrogen generating electrode) opposite the electrode (oxygen generating electrode) through which pure water flows, across the water electrolysis membrane electrode assembly, and passes through a separate flow path (not shown) before being discharged from the hydrogen electrode outlet hole (hydrogen electrode side outlet manifold) 14f. The oxygen generating electrode and the hydrogen generating electrode are both provided within the water electrolysis cell 10, but apart from the water electrolysis region 10a, separate flow paths are formed between the electrodes, separated from each other by a sealing member (not shown), to prevent the generated hydrogen and oxygen from mixing.

[0013] The structure of the water electrolysis cell 10 is described below. Fig. 2 is a partial cross-section taken along the line A-A in Fig. 1, illustrating the layer structure of the water electrolysis region 10a where water electrolysis is performed in the water electrolysis cell 10. Fig. 3 is a cross-section taken along the line B-B in Fig. 1, illustrating the layer structure of a portion of the oxygen electrode lead-out hole (oxygen electrode side outlet manifold) 14e, the oxygen electrode lead-out region 10e, the oxygen electrode lead-out side distribution region 10d, and a portion of the water electrolysis region 10a.

[0014] The water electrolysis cell 10 is made up of multiple layers, one of which serves as an oxygen evolution electrode (anode) and the other as a hydrogen evolution electrode (cathode) with a solid polymer electrolyte membrane 11 sandwiched therebetween. In the water electrolysis region 10a, as shown in FIG. 2 , the anode includes an anode catalyst layer 12, an anode gas diffusion layer 13, and an anode separator 14 stacked in this order from the solid polymer electrolyte membrane 11 side. On the other hand, the cathode includes a cathode catalyst layer 15, a cathode gas diffusion layer 16, and a cathode separator 17 stacked in this order from the solid polymer electrolyte membrane 11 side. Here, the water electrolysis membrane electrode assembly refers to a stack of the solid polymer electrolyte membrane 11, the anode catalyst layer 12 arranged on the anode side of the solid polymer electrolyte membrane 11, and the cathode catalyst layer 15 arranged 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 cells 10 in the water electrolysis region 10a is typically about 1.3 mm. As shown in FIG. 3, the water electrolysis cell 10 is provided with a frame 18 and a hydrogen reaction section 20 at both ends of the water electrolysis region 10a. First, the mode of each layer will be described, and then the layer structure in each region will be described.

[0015] 1.1. Aspects of each layer The layers included in the water electrolysis cell 10 may have the following configurations, for example: However, the water electrolysis cell of the present disclosure is not limited to these configurations.

[0016] [Solid polymer electrolyte membrane] The solid polymer electrolyte membrane 11 is one embodiment of an electrolyte membrane having proton conductivity. In this embodiment, the material (electrolyte) constituting the solid polymer electrolyte membrane 11 is a solid polymer material, such as a proton-conductive ion exchange membrane formed from a fluorine-based resin or a hydrocarbon-based resin material. This exhibits good proton conductivity (electrical conductivity) in a wet state. More specifically, a membrane made of Nafion (registered trademark), a perfluoro-based electrolyte, is exemplified. The thickness of the solid polymer electrolyte membrane 11 is not particularly limited, but is 200 μm or less, preferably 100 μm or less, and more preferably 30 μm or less.

[0017] [Anode catalyst layer] The anode catalyst layer (oxygen electrode catalyst layer) 12 is a catalyst layer containing at least one of a noble metal catalyst such as Pt, Ru, Ir, etc. and its oxides. More specifically, the catalyst may be Pt, iridium oxide, ruthenium oxide, iridium ruthenium oxide, or a mixture thereof. Examples of iridium oxides include iridium oxide (IrO2, IrO3), iridium tin oxide, and iridium zirconium oxide. Examples of ruthenium oxides include ruthenium oxide (RuO2, Ru2O3), ruthenium tantalum oxide, ruthenium zirconium oxide, ruthenium titanium oxide, and ruthenium titanium cerium oxide. Examples of iridium ruthenium oxides include iridium ruthenium cobalt oxide, iridium ruthenium tin oxide, iridium ruthenium iron oxide, and iridium ruthenium nickel oxide.

[0018] The anode catalyst layer 12 may contain an ionomer. The inclusion of an ionomer not only improves coating properties, but also facilitates the permeation of water supplied during water splitting due to its hydrophilicity. Examples of the ionomer that may be contained include ionomers containing perfluorinated electrolytes, which are electrolytes used in solid polymer electrolyte membranes.

[0019] [Anode gas diffusion layer] The anode gas diffusion layer 13 is a gas diffusion layer disposed on the anode side, and may be made of a material having gas permeability and conductivity, although known materials may be used. Specific examples include porous conductive materials made of a sintered body of metal fibers (e.g., titanium fibers) or metal particles (titanium particles).

[0020] [Anode separator] The anode separator 14 is a member (separator) that has a flow path (water supply flow path) 14a through which pure water and decomposed oxygen flow to be supplied to the anode gas diffusion layer 13. In this embodiment, the anode separator 14 is a plate-like member that is formed into a corrugated shape in the water electrolysis region 10a, with repeated projections and depressions, and the depressions 14c are placed in contact with the anode gas diffusion layer 13, thereby forming the water supply flow path 14a between the anode gas diffusion layer 13 and the projections 14b. The anode separator 14 can be produced by press-molding a titanium thin film, for example, and its thickness is typically 0.1 mm to 0.2 mm, and the height of the projections and recesses is typically about 0.5 mm.

[0021] As shown in FIG. 1 and described above, the anode separator 14 is provided with an oxygen electrode-side inlet manifold 14d, which is an inlet for pure water, an oxygen electrode-side outlet manifold 14e, which is an outlet for the generated oxygen and remaining water, and a hydrogen electrode-side outlet manifold 14f, which is an outlet for the generated hydrogen and produced water.

[0022] 3, the anode separator 14 of this embodiment is provided with a constricted portion 14g in the oxygen electrode lead-out region 10e so as to be convex toward the cathode separator 17. The constricted portion 14g functions as one of the structures that generates turbulence, thereby disrupting the flow of fluid on the surface of the anode separator 14 as will be described later, and promoting the hydrogen reaction in the hydrogen reaction unit 20.

[0023] In this embodiment, grooves 14h may be provided in the surface of the anode separator 14 facing the cathode separator 17 in the oxygen electrode outlet-side distribution region 10d and / or the oxygen electrode outlet region 10e connected thereto. The grooves 14h also function as one of the structures that generate turbulence, thereby disrupting the flow of fluid on the surface of the anode separator 14 as described below, and accelerating the hydrogen reaction in the hydrogen reaction unit 20. 4 to 6 are schematic diagrams showing examples of the grooves 14h. The direction of the straight arrows shown in FIGS. 4 to 6 corresponds to the direction indicated by H in FIG. The example in FIG. 4 has a shape in which the groove width changes in the direction in which the groove 14h extends. The example of FIG. 5 is a shape configured such that the positions of the grooves 14h are shifted in the groove width direction in the direction in which the grooves 14h extend. The example of FIG. 6 is an example in which adjacent grooves 14h join together in the direction in which the grooves 14h extend (grooves that separate midway may also be formed). Other examples of the structure that generates turbulence include a groove with a constant width that is linear in the direction in which the groove extends, a wavy shape, or an embossed uneven shape.

[0024] Furthermore, to reduce electrical contact resistance, a conductive layer may be provided on the front and back surfaces of the anode separator 14 at a location corresponding to the water electrolysis region 10a. The conductive layer may be made of any conductive material, such as platinum.

[0025] [Cathode catalyst layer] The cathode catalyst layer 15 is a catalyst layer containing a catalyst, and the catalyst contained in the cathode catalyst layer 15 can be a known catalyst, such as platinum, platinum-coated titanium, platinum-supported carbon, palladium-supported carbon, cobalt glyoxime, nickel glyoxime, etc. The cathode catalyst layer 15 may contain an ionomer. The inclusion of an ionomer can improve coating properties. Examples of the ionomer that can be contained include ionomers made of perfluoro-based electrolytes, which are electrolytes used in solid polymer electrolyte membranes.

[0026] [Cathode gas diffusion layer] The cathode gas diffusion layer 16 is a gas diffusion layer disposed on the cathode side, and may be made of a material having gas permeability and conductivity, such as a porous material such as carbon cloth or carbon paper.

[0027] [Cathode separator] The cathode separator 17 is a member having flow paths 17a through which hydrogen generated by the reduction of hydrogen ions and water (produced water) accompanying the hydrogen ions as they permeate the solid polymer electrolyte membrane 11 arrive. In this embodiment, the cathode separator 17 is a plate-like member formed into a corrugated shape in the water electrolysis region 10a, with repeated projections and depressions, and the recesses 17c are arranged in contact with the cathode gas diffusion layer 16, thereby forming flow paths 17a for discharging hydrogen between the cathode gas diffusion layer 16 and the projections 17b. The cathode separator 17 can be produced by press-molding a titanium thin film, for example, and the thickness thereof is typically 0.1 mm to 0.2 mm, and the height of the projections and recesses is typically about 0.5 mm.

[0028] As shown in FIG. 1 and described above, the cathode separator 17 is provided with an oxygen electrode side inlet manifold (not shown) that overlaps with the oxygen electrode side inlet manifold 14d, an oxygen electrode side outlet manifold (not shown) that overlaps with the oxygen electrode side outlet manifold 14e, and a hydrogen electrode side outlet manifold (not shown) that overlaps with the hydrogen electrode side outlet manifold 14f.

[0029] To reduce electrical contact resistance, a conductive layer may be provided on the front and back surfaces of the cathode separator 17 at a location corresponding to the water electrolysis region 10a. The conductive layer may be made of any conductive material, such as platinum.

[0030] Frame The frame 18 is disposed between the anode separator 14 and the cathode separator 17 at the outer periphery of the water electrolysis cell 10, and functions as a sealing member that seals the inside of the cell and separates the oxygen evolution electrode side from the hydrogen evolution electrode side. 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 outlet side dispersion region 10d, and the oxygen electrode outlet region 10e, and is disposed so as to be sandwiched between the anode separator 14 and the cathode separator 17. 3, the frame 18 is not sealed in that portion because it allows generated oxygen and residual water to flow from the water supply channel 14a of the anode separator 14 through the oxygen electrode outlet-side distribution region 10d and the oxygen electrode outlet region 10e to the oxygen electrode-side outlet manifold 14e. On the other hand, in the cross section of FIG. 3, it is sealed to block the flow of hydrogen from the channel 17a of the cathode separator 17 to the oxygen electrode-side inlet manifold 14e. In this way, the frame 18 adjusts its contact (seal) with the anode separator 14 and the cathode separator 17 to ensure appropriate fluid flow.

[0031] The frame 18 is made of a thermoplastic resin material that is electrically insulating, airtight, and has a relatively high melting point. Examples of such materials include crystalline polymers, more specifically, engineering plastics. Examples of engineering plastics include polyethylene naphthalate resin (PEN) and polyethylene terephthalate resin (PET). The thickness of the frame is not particularly limited, but is preferably 0.05 mm or more and 0.25 mm or less.

[0032] In this embodiment, a plurality of holes 18a may be provided in the frame 18 at a position that will become the oxygen electrode lead-out region 10e. An explanatory diagram is shown in Fig. 7. In Fig. 7, a diagram from the same perspective as Fig. 3 is shown at the top of the page, and a plan view of the frame 18 portion is shown at the bottom of the page. In this way, the portion of the frame 18 that leads to the oxygen electrode outlet manifold 14e at the position that becomes the oxygen electrode lead-out region 10d is not simply a single notch but is made up of multiple holes 18a. The multiple holes 18a function as a structure that generates turbulence, and as will be described later, disrupts the flow of fluid on the surface of the anode separator 14, thereby accelerating the hydrogen reaction in the hydrogen reaction unit 20.

[0033] [Hydrogen reaction section] The hydrogen reaction section 20 is a section where the hydrogen that has reached this point reacts with oxygen to convert it into water. Therefore, in this embodiment, a hydrogen reaction catalyst is disposed in the hydrogen reaction section 20, which promotes the reaction. The hydrogen reaction catalyst is not particularly limited, but platinum can be used, for example. When platinum is used, the film thickness is preferably 100 nm or less, and more preferably 30 nm or less, from the viewpoint of reducing the amount of precious metal used. The method for forming the platinum film is not particularly limited, but a so-called surface treatment method can be used, for example. Specific examples of surface treatment methods include ion plating, sputtering, and plating. The hydrogen reaction portions may be arranged so as to have a constant film thickness and cover the entire predetermined area, but are not limited to this, and may also be arranged in scattered island patterns or alternately in stripes.

[0034] The hydrogen reaction unit 20 is provided in a region where the generated oxygen and residual water flow. Specifically, the hydrogen reaction unit 20 may be provided on the inner surface of the flow path through which oxygen and residual water flow, in the oxygen electrode outlet-side distribution region 10d and / or the oxygen electrode outlet region 10e of the inner surface of the anode separator 14 (the surface on which the water electrolysis membrane electrode assembly is disposed), as shown in Fig. 3. Additionally or instead, the hydrogen reaction unit may be provided on the surface of the frame 18 (the surface on the oxygen electrode side). This allows the hydrogen mixed in the generated oxygen and the remaining water (permeated from the hydrogen evolution electrode side) to bind with oxygen on the inner surface of the flow path formed by the anode separator and react to form water. When the residual water discharged from the water electrolysis cell 10 is treated and then supplied back to the water electrolysis cell 10, the supplied water may contain hydrogen. Therefore, a hydrogen reaction section may also be provided in the flow path of the oxygen electrode inlet region 10c and the subsequent oxygen electrode inlet-side distribution region 10c.

[0035] 1.2. Layer composition of water electrolysis region 2, the layer structure of the water electrolysis region 10a is such that the anode comprises an anode catalyst layer 12, an anode gas diffusion layer 13, and an anode separator 14 stacked in this order from the solid polymer electrolyte membrane 11 side. On the other hand, the cathode comprises a cathode catalyst layer 15, a cathode gas diffusion layer 16, and a cathode separator 17 stacked in this order from the solid polymer electrolyte membrane 11 side. The anode separator 14 has a flow path (water supply flow path) 14a through which pure water and decomposed oxygen flow to be supplied to the anode gas diffusion layer 13. In this embodiment, the anode separator 14 is a plate-like member formed in a corrugated shape in the water electrolysis region 10a, with repeated projections and depressions, and the depressions 14c are disposed in contact with the anode gas diffusion layer 13, thereby forming the water supply flow path 14a between the anode gas diffusion layer 13 and the projections 14b. The cathode separator 17 has flow paths 17a through which hydrogen generated by the reduction of hydrogen ions and water (produced water) accompanying the hydrogen ions as they permeate the solid polymer electrolyte membrane 11 arrive. In this embodiment, the cathode separator 17 is a plate-like member formed in a corrugated shape in the water electrolysis region 10a, with repeated projections and depressions, and the depressions 17c are arranged in contact with the cathode gas diffusion layer 16, thereby forming flow paths 17a for discharging hydrogen between the cathode gas diffusion layer 16 and the projections 17b.

[0036] 1.3. Layer structure of the oxygen electrode outlet distribution region and oxygen electrode outlet region The oxygen electrode outlet distribution region 10d and the oxygen electrode outlet region 10e are regions through which the oxygen produced in the water electrolysis region 10a and the remaining water pass before being discharged to the oxygen electrode side outlet manifold 14e. As can be seen from FIG. 3 , the oxygen electrode outlet-side distribution region 10d has end faces of the solid polymer electrolyte membrane 11, anode catalyst layer 12, anode gas diffusion layer 13, cathode catalyst layer 15, and cathode gas diffusion layer 16. The end face of the anode gas diffusion layer 13 is formed slightly recessed from the other end faces. A frame 18 is laminated on the anode catalyst layer 12 and extends from the end face of the anode gas diffusion layer 13. The frame 18 reaches the inside of the oxygen electrode outlet region 10e and extends to the oxygen electrode outlet manifold 14e. In the oxygen electrode outlet-side distribution region 10d, the cathode separator 17 is bent in the thickness direction (the stacking direction of the layers) until it contacts the surface of the frame 18, and the hydrogen evolution electrode side is sealed. In the oxygen electrode lead-out region 10e, a narrowed portion 14g is formed so that the anode separator 14 is bent so as to approach the frame 18, and the flow path is narrowed in the thickness direction. In this embodiment, as described above, in the oxygen electrode outlet-side distribution region 10d and the oxygen electrode outlet region 10e, the hydrogen reaction section 20 is disposed on the surface of the flow path formed by the anode separator 14 on the frame 18 side.

[0037] 1.4. Effects etc. The water electrolysis cell 10 of the present disclosure operates, for example, as follows. When pure water is supplied from the oxygen electrode side inlet manifold 14d, it passes through the oxygen electrode introduction region 10b and the oxygen electrode introduction side distribution region 10c and reaches the water electrolysis region 10a. In the water electrolysis region 10a, pure water (HO) supplied to the anode (oxygen evolving electrode) from the water supply channel 14a is converted into oxygen, electrons, and protons (H + ). At this time, the protons pass through the solid polymer electrolyte membrane 11 and move to the cathode catalyst layer 15. Meanwhile, the electrons separated in the anode catalyst layer 12 pass through an external circuit and reach the cathode catalyst layer 15. Then, the protons receive the electrons in the cathode catalyst layer 15, generating hydrogen (H2), which then reaches the cathode gas diffusion layer 16. In the cathode gas diffusion layer 16, produced water is present along with the generated hydrogen gas.

[0038] The hydrogen gas and accompanying water present in the cathode gas diffusion layer 16 reach the cathode separator 17, flow through the flow passage 17a, and are discharged from the hydrogen electrode side outlet manifold 14f (hydrogen electrode lead-out hole).

[0039] On the other hand, oxygen generated in the anode catalyst layer 12 and residual water that has not been used return to the anode separator 14, pass through the hydrogen supply flow path 14a, pass through the flow paths of the oxygen electrode outlet-side distribution region 10d and the oxygen electrode outlet region 10e, and are discharged from the oxygen electrode outlet manifold 14e. Here, hydrogen that has permeated from the hydrogen generating electrode side may be mixed into the residual water discharged from the hydrogen supply flow path 14a. In response to this, the water electrolysis cell 10 of the present disclosure is provided with the hydrogen reaction unit 20 on the inner surface of the flow path in the oxygen electrode outlet-side distribution region 10d and the oxygen electrode outlet region 10e, as described above, where the mixed hydrogen can be converted into water by reacting with oxygen. This reduces the amount of hydrogen contained in the residual water collected downstream, eliminating the need for or reducing the scale of additional hydrogen treatment equipment. This also simplifies management of the gas to be treated. As in the above-described embodiment, by providing a structure that generates turbulence, such as the throttle section 14g, the groove 14h, and the hole 18a in the frame 18, the flow of the remaining water is disturbed, making it easier for the mixed hydrogen and generated oxygen to reach the hydrogen reaction section 20, and they can be efficiently converted into water.

[0040] In the water electrolysis cell 10 described above, the supplied pure water basically flows in one direction (from right to left on the page) through the water electrolysis region 10a. However, as shown by the straight arrows in FIG. 8 , a partition may be provided so that the pure water flows in a turning manner at the distribution regions 10c and 10d provided at both ends of the water electrolysis region 10a.

[0041] 2. Water electrolysis stack 2.1. Basic structure of water electrolysis stack The water electrolysis stack 30 is a component formed by stacking multiple (approximately 50 to 400) of the above-described water electrolysis cells 10, and generates hydrogen and oxygen by passing electricity through the multiple water electrolysis cells 10. An outline of the configuration is shown in Figure 9. The water electrolysis stack 30 includes a stack case 31, end plates 32, multiple water electrolysis cells 10, and a biasing member 33.

[0042] The stack case 31 is a housing that houses a plurality of stacked water electrolysis cells 10 and the biasing member 33. In this embodiment, the stack case 31 is a rectangular cylinder with one open end and the other closed end, and a plate-like piece protrudes along the edge of the opening to the opposite side to the opening, forming a flange 31a.

[0043] The end plate 32 is a plate-shaped member that closes the opening of the stack case 31. The end plate 32 is fixed to the stack case 31 with bolts, nuts, etc. at the portion where it overlaps with the flange 31a of the stack case 31 so as to cover the stack case 21.

[0044] The water electrolysis cell 10 is as described above. A plurality of such water electrolysis cells 10 are stacked. In this embodiment, as can be seen from Fig. 9 , the water electrolysis cells 10 are stacked horizontally, and each water electrolysis cell 10 is arranged such that the direction in which the water supply flow paths 14a and the direction in which the flow paths 17a are arranged are vertical, as shown in Fig. 1 .

[0045] The biasing member 33 is housed inside the stack case 31 and applies a pressing force in the stacking direction to the stack of water electrolysis cells 10. An example of the biasing member is a disc spring.

[0046] 2.2.Layer structure of water electrolysis cell As described above, the water electrolysis stack 30 is formed by stacking a plurality of water electrolysis cells 10. Figure 10 shows a cross section of a portion (part of the water electrolysis region 10a) of three of the stacked water electrolysis cells 10.

[0047] 10 , when the water electrolysis cells 10 are stacked, the cathode separator 17 of one water electrolysis cell 10 overlaps with the anode separator 14 of the other adjacent water electrolysis cell 10. More specifically, the protrusion 17b of the cathode separator 17 of one water electrolysis cell 10 and the protrusion 14b of the anode separator 14 of the other water electrolysis cell 10 come into contact with each other and overlap.

[0048] As described above, in this embodiment, hydrogen is converted into water by reacting with oxygen in each of the water electrolysis cells 10. Therefore, even a water electrolysis stack in which many water electrolysis cells 10 are stacked can achieve the above-described effects, and the greater the number of water electrolysis cells 10 stacked, the more significant the effects become.

[0049] 2.3.Other examples Fig. 11 is a diagram illustrating another embodiment. Fig. 11 shows a water electrolysis stack (i.e., a state in which a plurality of water electrolysis cells 10 are stacked) from the same perspective as Fig. 3. Fig. 11 shows one water electrolysis cell 10 and a portion of another water electrolysis cell 10 stacked thereon.

[0050] In this embodiment, a sealant 40 is disposed between the anode separator 14 and the frame 18 in the oxygen electrode lead-out region 10e, and is configured so as not to communicate with the oxygen electrode-side outlet manifold 14e. Instead, in this embodiment, a hole 14j is provided in the oxygen electrode lead-out region 10e of the anode separator 14, forming a flow path between the anode separator 14 and the cathode separator 17 of the adjacent water electrolysis cell 10, and this flow path is configured to communicate with the oxygen electrode-side outlet manifold 14e. In this case, the generated oxygen and residual water are bent midway as indicated by the straight arrows, causing their flow to become disturbed. Therefore, by providing a hydrogen reaction section 20 on the inner surface of the flow path formed by the anode separator 14 and the cathode separator 17 of the adjacent water electrolysis cell 10 as shown in Figure 11, the mixed hydrogen can be efficiently reacted with oxygen. This configuration also achieves the above-mentioned effects. [Explanation of symbols]

[0051] 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 evolution electrode gas diffusion layer), 14...anode separator (oxygen evolution 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...throttling 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 evolution electrode gas diffusion layer), 17...cathode separator (hydrogen evolution electrode separator), 18...frame, 20...hydrogen reaction portion (portion having hydrogen reaction catalyst), 30...water electrolysis stack

Claims

1. A water electrolysis cell comprising an electrolyte membrane, a catalyst layer, and a separator through which a fluid flows, and which generates hydrogen and oxygen by supplying water and applying a voltage, a hydrogen reaction catalyst that promotes the reaction between hydrogen and oxygen is provided at a portion of the surface of the separator on the oxygen generating electrode side through which the generated oxygen and the remaining water flow; water electrolysis cell.

2. 2. The water electrolysis cell according to claim 1, further comprising a structure for generating turbulence in the remaining water at a location where the hydrogen reaction catalyst is disposed.

3. 3. The water electrolysis cell according to claim 2, wherein the structure for generating turbulence is a groove and / or an embossment provided in a discharge area that is a region leading to a discharge hole for the remaining water.

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