Water electrolysis steril

Abstract

To provide a water electrolysis cell capable of preventing an electrolyte membrane from breaking.SOLUTION: The water electrolysis cell comprises an electrolyte membrane, two catalyst layers, two microporous layers, two gas diffusion layers, and two separators, with the electrolyte membrane interposed between the two catalyst layers, in which the microporous layers are each disposed adjacent to the catalyst layer surface disposed opposite to the electrolyte membrane, the gas diffusion layers are each disposed adjacent to the microporous layer surface disposed opposite to the catalyst layer, and the separators are each disposed adjacent to the gas diffusion layer surface disposed opposite to the microporous layer, and the water electrolysis cell is such that the surface area of either of an oxygen electrode and a hydrogen electrode is smaller than that of the other, and the adhesion strength between the microporous layers and the corresponding catalyst layers is greater than the adhesion strength between the gas diffusion layers and the corresponding microporous layers, respectively.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Various studies have been conducted on water electrolysis devices. For example, Patent Document 1 discloses a differential pressure type high-pressure water electrolysis device characterized in that the electrolyte membrane and the insulating reinforcing member are joined together with an adhesive at the overlapping portions along the stacking direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-203188 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to increase the pressure of hydrogen produced by water electrolysis, there is a need to make the pressure of the hydrogen electrode in a water electrolysis cell higher than the pressure of the oxygen electrode. However, in a water electrolysis cell having a stepped structure at the end of the electrode part, there is a problem that the electrolyte membrane bends due to the pressure difference between the hydrogen electrode and the oxygen electrode during long-term operation of the water electrolysis cell, making the electrolyte membrane more susceptible to rupture and causing leakage.

[0005] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a water electrolysis cell that can suppress the occurrence of rupture of the electrolyte membrane. [Means for solving the problem]

[0006] The present disclosure provides a water electrolysis cell, comprising: the water electrolysis cell includes an electrolyte membrane, two catalyst layers, two microporous layers, two gas diffusion layers, and two separators; the electrolyte membrane is sandwiched between the two catalyst layers, Each of the microporous layers is disposed adjacent to a surface of each of the catalyst layers opposite to the electrolyte membrane side, Each of the gas diffusion layers is disposed adjacent to a surface of each of the microporous layers opposite to the catalyst layer side, Each of the separators is disposed adjacent to a surface of each of the gas diffusion layers opposite to the microporous layer side, In the water electrolysis cell, one of the oxygen electrode and the hydrogen electrode has an area smaller than the other, The water electrolysis cell is provided in which the adhesive strength between each of the microporous layers and each of the catalyst layers is higher than the adhesive strength between each of the gas diffusion layers and each of the microporous layers.

[0007] In the present disclosure, the pore size of each of the gas diffusion layers may be 10 μm or more and 100 μm or less. [Effects of the Invention]

[0008] The water electrolysis cell of the present disclosure can suppress the occurrence of rupture of the electrolyte membrane. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a partial cross-sectional schematic view illustrating an example of a portion of a water electrolysis cell according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiments of the present disclosure are described below. It should be noted that matters necessary for implementing the present disclosure other than those specifically mentioned in this specification (e.g., the general configuration and manufacturing process of a water electrolysis cell that do not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field. Furthermore, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. Any combination of upper and lower limits in the numerical range can be adopted.

[0011] The present disclosure provides a water electrolysis cell, comprising: the water electrolysis cell includes an electrolyte membrane, two catalyst layers, two microporous layers, two gas diffusion layers, and two separators; the electrolyte membrane is sandwiched between the two catalyst layers, Each of the microporous layers is disposed adjacent to a surface of each of the catalyst layers opposite to the electrolyte membrane side, Each of the gas diffusion layers is disposed adjacent to a surface of each of the microporous layers opposite to the catalyst layer side, Each of the separators is disposed adjacent to a surface of each of the gas diffusion layers opposite to the microporous layer side, In the water electrolysis cell, one of the oxygen electrode and the hydrogen electrode has an area smaller than the other, The water electrolysis cell is provided in which the adhesive strength between each of the microporous layers and each of the catalyst layers is higher than the adhesive strength between each of the gas diffusion layers and each of the microporous layers.

[0012] The water electrolysis cell includes an electrolyte membrane, two catalyst layers, two microporous layers (MPLs), two gas diffusion layers (GDLs), and two separators. The water electrolysis cell of the present disclosure electrolyzes water supplied to the anode (oxygen electrode), generating oxygen from the anode and hydrogen from the cathode (hydrogen electrode) as follows. Anode: H2O → 2H + + 1 / 2O2+ 2e - Cathode: 2H + + 2e - → H2

[0013] The water electrolysis cell includes an electrode unit. The electrode section has, in this order, an anode gas diffusion layer, an anode microporous layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, a cathode microporous layer, and a cathode gas diffusion layer. In the present disclosure, the anode catalyst layer-electrolyte membrane-cathode catalyst layer assembly is referred to as CCM.

[0014] The cathode (hydrogen electrode) includes a cathode catalyst layer, a cathode-side microporous layer, and a cathode-side gas diffusion layer. The anode (oxygen electrode) includes an anode catalyst layer, an anode-side microporous layer, and an anode-side gas diffusion layer. In the water electrolysis cell, one of the oxygen electrode and the hydrogen electrode may have a smaller area than the other, and the area of ​​the oxygen electrode may be smaller than the area of ​​the hydrogen electrode, so that the electrode parts of the water electrolysis cell have a stepped structure at their end portions in the planar direction. The catalytic layer, microporous layer, and gas diffusion layer of the electrode having the smaller area, either the oxygen electrode or the hydrogen electrode, may have an area smaller than that of the electrolyte membrane. The catalytic layer, microporous layer, and gas diffusion layer of the electrode having the smaller area, either the oxygen electrode or the hydrogen electrode, are not particularly limited as long as they have an area smaller than that of the electrolyte membrane. In the water electrolysis cell of the present disclosure, the pressure of the hydrogen electrode in the water electrolysis cell may be higher than the pressure of the oxygen electrode.

[0015] The cathode catalyst layer and the anode catalyst layer are collectively referred to as catalyst layers. The catalyst layer may include, for example, a catalytic metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, and a carrier having electron conductivity. Examples of catalyst metals that can be used include iridium (Ir), ruthenium (Ru), platinum (Pt), and alloys of Pt with other metals (e.g., Pt alloys mixed with cobalt and nickel). The anode catalyst layer may use, for example, Ir and Ru as the catalyst metal, and the cathode catalyst layer may use, for example, Pt and Pt alloys as the catalyst metal. The electrolyte may be a fluorine-based resin, etc. As the fluorine-based resin, for example, a Nafion solution may be used. The catalytic metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalytic metal (catalyst-supported carrier) and the electrolyte may be mixed together. Examples of the carrier for supporting the catalytic metal include carbon materials such as carbon, which are generally available commercially.

[0016] The electrolyte membrane is sandwiched between two catalyst layers: one is a cathode catalyst layer and the other is an anode catalyst layer. The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of the solid polymer electrolyte membrane include a fluorine-based electrolyte membrane such as a thin film of perfluorosulfonic acid containing water, and a hydrocarbon-based electrolyte membrane. The electrolyte membrane may be, for example, a Nafion membrane (manufactured by DuPont).

[0017] The anode-side microporous layer and the cathode-side microporous layer are collectively referred to as the microporous layer. The anode-side microporous layer and the cathode-side microporous layer are disposed adjacent to the surface of each catalyst layer opposite the electrolyte membrane side. That is, the anode-side microporous layer is disposed adjacent to the surface of the anode catalyst layer opposite the electrolyte membrane side. The cathode-side microporous layer is disposed adjacent to the surface of the cathode catalyst layer opposite the electrolyte membrane side. 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 of 1 to several hundred μm.

[0018] The cathode side gas diffusion layer and the anode side gas diffusion layer are collectively referred to as gas diffusion layers. The cathode-side gas diffusion layer and the anode-side gas diffusion layer are disposed adjacent to the surface of each microporous layer opposite the catalyst layer side. That is, the cathode-side gas diffusion layer is disposed adjacent to the surface of the cathode-side microporous layer opposite the cathode catalyst layer side. The anode-side gas diffusion layer is disposed adjacent to the surface of the anode-side microporous layer opposite the anode catalyst layer side. The gas diffusion layer may be a gas-permeable, i.e., porous, electrically conductive member or the like. Examples of the conductive member include porous carbon materials such as carbon cloth and carbon paper, and porous metal materials such as metal mesh and foam metal.

[0019] The anode separator and cathode separator are collectively referred to as separators. The anode separator and cathode separator are disposed adjacent to the surface of each gas diffusion layer opposite the microporous layer side. That is, the cathode separator is disposed adjacent to the surface of the cathode-side gas diffusion layer opposite the cathode-side microporous layer side. The anode separator is disposed adjacent to the surface of the anode-side gas diffusion layer opposite the anode-side microporous layer side. The two separators, the anode separator and the cathode separator, sandwich the resin frame and the electrode portion. The separator may have holes such as supply holes and discharge holes for circulating fluids such as reaction water, oxygen, hydrogen, and a cooling medium in the stacking direction of the water electrolysis cells. The reaction water and the cooling medium may be water or the like. The supply holes include an anode supply hole, a cathode supply hole, and a coolant supply hole. Examples of the exhaust holes include an anode exhaust hole, a cathode exhaust hole, and a coolant exhaust hole. The separator may have flow paths for reaction fluids such as reaction water, oxygen, hydrogen, etc. on the surface in contact with the gas diffusion layer. The separator may also have flow paths for a cooling medium for maintaining a constant temperature of the water electrolysis cell on the surface opposite to the surface in contact with the gas diffusion layer. The anode separator may have a flow path for anode fluid such as reaction water, oxygen, etc. on the surface in contact with the anode-side gas diffusion layer. The anode separator may also have a flow path for a cooling medium for maintaining a constant temperature of the water electrolysis cell on the surface opposite to the surface in contact with the anode-side gas diffusion layer. The cathode separator may have a flow path for a cathode fluid such as hydrogen on the surface in contact with the cathode-side gas diffusion layer, and may have a flow path for a cooling medium for maintaining a constant temperature of the water electrolysis cell on the surface opposite to the surface in contact with the cathode-side gas diffusion layer. The separator may be a gas-impermeable conductive material, etc. Examples of the conductive material include dense carbon made gas-impermeable by compressing a resin material such as a thermosetting resin, a thermoplastic resin, or a resin fiber, and a carbon material such as a carbon powder or a carbon fiber, and a press-molded metal (e.g., titanium, stainless steel, etc.) plate. The shape of the separator may be rectangular, horizontally elongated hexagonal, horizontally elongated octagonal, circular, oval, or the like.

[0020] The water electrolysis cell may typically have a resin frame. The resin frame is disposed around the outer periphery of the electrode unit and is disposed between the cathode separator and the anode separator. The resin frame may have a skeleton, an opening, and a hole. The skeleton is the main part of the resin frame that is connected to the electrode portion. The opening is a holding area for the electrode unit, and is an area that penetrates a part of the skeleton to accommodate the electrode unit. The opening may be located in the resin frame at a position where the skeleton is disposed around (the outer periphery of) the electrode unit, or may be located in the center of the resin frame. The holes in the resin frame allow fluids such as reaction water, oxygen, hydrogen, and a cooling medium to circulate in the stacking direction of the water electrolysis cells. The holes in the resin frame may be aligned with the holes in the separators so as to communicate with each other. The resin frame may include a frame-shaped core layer and two frame-shaped shell layers, that is, a first shell layer and a second shell layer, provided on both sides of the core layer. The first and second shell layers may be provided in a frame shape on both sides of the core layer, similarly to the core layer.

[0021] The core layer may be a structural member having gas sealing and insulating properties, and may be formed of a material whose structure does not change even under the temperature conditions of thermocompression bonding in the manufacturing process of the water electrolysis cell. Specifically, the core layer may be made of a resin 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 (polyethersulfone), PPSU (polyphenylsulfone), LCP (liquid crystal polymer), or epoxy resin. The core layer may also be made of a rubber material such as EPDM (ethylene propylene diene rubber), fluororubber, or silicone rubber. The thickness of the core layer may be 5 μm or more, or 20 μm or more, from the viewpoint of ensuring insulation, and may be 200 μm or less, or 150 μm or less, from the viewpoint of reducing the thickness of the water electrolysis cell.

[0022] The first and second shell layers may have properties such as high adhesiveness to other substances, softening under the temperature conditions during thermocompression bonding, and lower viscosity and melting point than the core layer in order to bond the core layer to the anode separator and the cathode separator and ensure sealing. Specifically, the first and second shell layers may be made of a thermoplastic resin such as a polyester or modified olefin resin, or a thermosetting resin such as a modified epoxy resin. 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 resin. By providing shell layers on both sides of the core layer, bonding between the resin frame and the two separators by hot pressing becomes easier. 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 ensuring adhesiveness, and may be 100 μm or less, or 40 μm or less, from the viewpoint of reducing the thickness of the water electrolysis cell.

[0023] In the resin frame, the first shell layer and the second shell layer may be provided only in the portions that bond to the anode separator and the cathode separator, respectively. The first shell layer provided on one surface of the core layer may be bonded to the cathode separator. The second shell layer provided on the other surface of the core layer may be bonded to the anode separator. The resin frame may then be sandwiched between a pair of separators.

[0024] In the present disclosure, the adhesive strength between each microporous layer and each catalyst layer is higher than the adhesive strength between each gas diffusion layer and each microporous layer, and the adhesive strength between each microporous layer and each catalyst layer may be 1.4 times or more higher than the adhesive strength between each gas diffusion layer and each microporous layer. In the present disclosure, the adhesive strength between the anode-side microporous layer and the anode catalyst layer may be the same as the adhesive strength between the cathode-side microporous layer and the cathode catalyst layer. In the present disclosure, the adhesive strength between the anode side gas diffusion layer and the anode side microporous layer may be the same as the adhesive strength between the cathode side gas diffusion layer and the cathode side microporous layer. Conventionally, the adhesive strength between the microporous layer and the catalyst layer was equal to or less than the adhesive strength between the gas diffusion layer and the microporous layer. In contrast, in the present disclosure, the adhesive strength between the microporous layer and the catalyst layer is made stronger than the adhesive strength between the gas diffusion layer and the microporous layer, which results in a structure in which the catalyst layer is reinforced by the microporous layer (MPL) in a water electrolysis cell with high gas pressure on the hydrogen electrode side, thereby preventing bending of the electrolyte membrane. To achieve the above-mentioned adhesive strength, the pore size of the GDL may be 100 μm or less from the viewpoint of suppressing penetration of the MPL into the GDL during MPL formation and reducing the adhesive strength between the MPL and GDL.From the viewpoint of releasing hydrogen, the pore size may be 10 μm or more. To prevent the MPL from penetrating into the hydrophobic GDL and reduce the adhesive strength between the MPL and GDL, the coating liquid for the MPL during MPL formation may be an aqueous solution. The aqueous solution may be a mixture of water-soluble polytetrafluoroethylene (PTFE) and a dispersant. Examples of dispersants include surfactants having a perfluoroalkyl group manufactured by AGC, non-fluorinated dispersants manufactured by Sekisui Chemical, Leocol (registered trademark) manufactured by Lion Corporation, fluororesin dispersant "Ftergent" manufactured by Neos, D-111 manufactured by Daikin Industries, and N1310 (trade name) manufactured by Nippon Nyukazai.

[0025] In the present disclosure, from the viewpoint of facilitating the transfer of protons, the adhesive strength between the electrolyte membrane and each catalyst layer may be higher than the adhesive strength between each gas diffusion layer and each microporous layer. In the present disclosure, the adhesive strength between the electrolyte membrane and each catalyst layer may be the same as the adhesive strength between each microporous layer and each catalyst layer. In the present disclosure, the adhesive strength between the electrolyte membrane and the anode catalyst layer may be the same as the adhesive strength between the electrolyte membrane and the cathode catalyst layer.

[0026] FIG. 1 is a partial cross-sectional schematic view showing an example of a portion of a water electrolysis cell according to the present disclosure. As shown in FIG. 1, a water electrolysis cell 100 according to the present disclosure includes an electrode assembly 10, a resin frame 20, and an anode separator 30 and a cathode separator 40 that sandwich the electrode assembly 10 and the resin frame 20. The electrode section 10 has an anode gas diffusion layer 11, an anode microporous layer 12, an anode catalyst layer 13, an electrolyte membrane 14, a cathode catalyst layer 15, a cathode microporous layer 16, and a cathode gas diffusion layer 17 in this order. The areas of the anode-side gas diffusion layer 11, anode-side microporous layer 12, and anode catalyst layer 13 that constitute the oxygen electrode are smaller than the areas of the electrolyte membrane 14 and the cathode catalyst layer 15, cathode-side microporous layer 16, and cathode-side gas diffusion layer 17 that constitute the hydrogen electrode. As a result, the electrode unit 10 of the water electrolysis cell 100 has a stepped structure at the end in the planar direction. A part of the resin frame 20 may be disposed on the end of the electrolyte membrane 14. Although not shown, the resin frame 20 is disposed so as to surround the electrode assembly 10 in a plan view. The water electrolysis cell 100 is designed so that the adhesive strength between each of the microporous layers 12, 16 and each of the catalyst layers 13, 17, and the adhesive strength between the electrolyte membrane 14 and each of the catalyst layers 13, 17 are higher than the adhesive strength between each of the gas diffusion layers 11, 15 and each of the microporous layers 12, 16. This provides a structure in which the catalyst layers 13, 17 are reinforced by the microporous layers 12, 16 in the water electrolysis cell 100, which has a high gas pressure on the hydrogen electrode side. This prevents the electrolyte membrane 14 from bending and breaking even when the pressure at the hydrogen electrode in the water electrolysis cell 100 is made higher than the pressure at the oxygen electrode. [Example]

[0027] Example 1 A water electrolysis cell was prepared having electrode parts in which the adhesive strength between each microporous layer, each catalyst layer, and the electrolyte membrane was 1.4 times higher than the adhesive strength between each gas diffusion layer and each microporous layer. The pressure at the hydrogen electrode of the water electrolysis cell was set to 0.9 MPa abs and the pressure at the oxygen electrode was set to 0.1 MPa abs, and the time until leakage occurred was measured. The results are shown in Table 1.

[0028] <Comparative Example 1> A water electrolysis cell was prepared having an electrode part in which the adhesive strength between each microporous layer, each catalyst layer, and the electrolyte membrane was lower than the adhesive strength between each gas diffusion layer and each microporous layer, and the time until leakage occurred was measured for the water electrolysis cell in the same manner as in Example 1. The results are shown in Table 1.

[0029] [Table 1]

[0030] It was confirmed that no leakage occurred even after 100 hours or more in the water electrolysis cell of Example 1. This shows that the configuration of the present disclosure can prevent the electrolyte membrane from bending and breaking, even when the pressure at the hydrogen electrode in the water electrolysis cell is made higher than the pressure at the oxygen electrode, thereby reducing the occurrence of leakage. [Explanation of symbols]

[0031] 10 Electrode part 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 20 Resin frame 30 Anode separator 40 Cathode separator 100 water electrolysis cell

Claims

[Claim 1] A method for manufacturing a water electrolysis cell, comprising: the water electrolysis cell includes an electrolyte membrane, two catalyst layers, two microporous layers, two gas diffusion layers, and two separators; the electrolyte membrane is sandwiched between the two catalyst layers, Each of the microporous layers is disposed adjacent to a surface of each of the catalyst layers opposite to the electrolyte membrane side, Each of the gas diffusion layers is disposed adjacent to a surface of each of the microporous layers opposite to the catalyst layer side, Each of the separators is disposed adjacent to a surface of each of the gas diffusion layers opposite to the microporous layer side, In the water electrolysis cell, one of the oxygen electrode and the hydrogen electrode has an area smaller than the other, the gas diffusion layer is a conductive member having pores, The pore diameter of each of the gas diffusion layers is 10 μm or more and 100 μm or less, forming the microporous layer by applying a coating liquid to a surface of the gas diffusion layer opposite to the separator side; The coating liquid is an aqueous solution, the aqueous solution is a mixture of polytetrafluoroethylene and a dispersant, The method for producing a water electrolysis cell, wherein the dispersant is a surfactant having a perfluoroalkyl group.

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