Water electrolyser, water electrolyser set, and method for manufacturing water electrolyser

Abstract

Embodiments provide a water electrolyser capable of maintaining proton conductivity without containing an organofluorine compound. A water electrolyser according to an embodiment of the present invention is provided with: an anode electrode including an anode catalyst layer in which anode catalyst sheets, which contain iridium and are formed in the form of nanosheets, are laminated with a gap therebetween; a cathode electrode including a cathode catalyst layer in which cathode catalyst sheets, which contain platinum and are formed in the form of nanosheets, are laminated with a gap therebetween; and an electrolyte membrane that is disposed between the anode electrode and the cathode electrode and contains a hydrocarbon-based material.

Description

[0001] Reference to relevant applications

[0002] This application claims priority based on Japanese Patent Application No. 2024-081225 (filed on May 17, 2024). This application incorporates the entire contents of that basic application by reference. Technical Field

[0003] The embodiments relate to a water electrolyzer, a water electrolyzer assembly, and a method for manufacturing a water electrolyzer. Background Technology

[0004] In recent years, research on electrochemical cells has been very active. Among electrochemical cells, the application of solid polymeric water electrolyzers (PEMECs) in hydrogen generation in large-scale energy storage systems is highly anticipated.

[0005] In the operation of a water electrolysis device using a water electrolyzer, a direct current is passed into the electrolyzer to electrolyze the water supplied to the anode electrode. This generates hydrogen ions (protons) at the anode electrode. The hydrogen ions then move through the electrolyte membrane to the cathode electrode, where they generate hydrogen.

[0006] In water electrolyzers, a catalyst layer is provided to promote the electrolysis reaction. Perfluorosulfonic acid (PFSA) is typically used in this catalyst layer as an ionomer to improve proton conductivity. PFSA belongs to the category of organofluorine compounds (PFAS) with relatively broad restrictions due to their harmful effects on the environment and human health. Summary of the Invention

[0007] The problem to be solved by the present invention is to provide a water electrolyzer, a water electrolyzer assembly, and a method for manufacturing a water electrolyzer that can maintain proton conductivity without containing organic fluorine compounds.

[0008] The water electrolyzer of the embodiment includes: an anode electrode comprising an anode catalyst layer formed by stacking anode catalyst sheets containing iridium and formed in nanosheet form with gaps; a cathode electrode comprising a cathode catalyst layer formed by stacking cathode catalyst sheets containing platinum and formed in nanosheet form with gaps; and an electrolyte membrane disposed between the anode electrode and the cathode electrode, and containing a hydrocarbon material.

[0009] The water electrolysis cell assembly of the embodiment includes the water electrolysis cell described above.

[0010] The method for manufacturing a water electrolyzer according to the embodiment includes the following steps: a step of preparing an anode electrode, the anode electrode comprising an anode catalyst layer formed by stacking anode catalyst sheets containing iridium and formed in nanosheet form with gaps; a step of preparing a cathode electrode, the cathode electrode comprising a cathode catalyst layer formed by stacking cathode catalyst sheets containing platinum and formed in nanosheet form with gaps; a step of preparing an electrolyte membrane containing a hydrocarbon material; and a step of simultaneously disposing the electrolyte membrane between the anode electrode and the cathode electrode and bonding the anode electrode and the cathode electrode to the electrolyte membrane.

[0011] Invention Effects

[0012] According to the implementation method, proton conductivity can be maintained without containing organofluorine compounds. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating an example of a water electrolysis apparatus according to this embodiment.

[0014] Figure 2 It means Figure 1 The diagram shows a schematic representation of the structure of a water electrolysis cell assembly.

[0015] Figure 3 It means Figure 2 The diagram shows a schematic cross-sectional view of the general structure of a water electrolysis cell. Detailed Implementation

[0016] Hereinafter, the water electrolyzer, water electrolyzer assembly, and water electrolyzer manufacturing method of this embodiment will be described with reference to the accompanying drawings.

[0017] First, adopt Figure 1 An example of a water electrolysis apparatus using the water electrolysis cell group of this embodiment will be described.

[0018] like Figure 1 As shown, the water electrolysis device 1 is an example of an apparatus that uses the electrolyte membrane 33 described later to generate hydrogen and oxygen. The water electrolysis device 1 includes a water electrolysis cell assembly 20, a water tank 2, a supply pump 3, a gas-liquid separator 4, a water inlet manifold 5, a water outlet manifold 6, a circulation pump 7, a hydrogen manifold 8, a hydrogen gas-liquid separator 9, a dehumidifier 10, a power supply unit 11, and a control unit 12.

[0019] like Figure 2 As shown, the water electrolyzer assembly 20 is constructed by stacking multiple water electrolyzers 30. More specifically, the water electrolyzer assembly 20 includes multiple water electrolyzers 30, multiple diaphragms 21, an anode current collector 22, and a cathode current collector 23. The water electrolyzers 30, diaphragms 21, anode current collector 22, and cathode current collector 23 are securely pressed together by a pair of fastening plates (not shown).

[0020] The water electrolyzer 30 includes an anode electrode 31, a cathode electrode 32, and an electrolyte membrane 33. The water electrolyzer 30 is also referred to as a membrane electrode assembly.

[0021] like Figure 2 As shown, the diaphragm 21 is sandwiched between two water electrolysis cells 30. An anode flow path 24 is formed on the surface of the diaphragm 21 that contacts the anode electrode 31. The anode flow path 24 can be composed of multiple trenches. A cathode flow path 25 is formed on the surface of the diaphragm 21 that contacts the cathode electrode 32. The cathode flow path 25 can also be composed of multiple trenches. The diaphragm 21 can be both conductive and impermeable to air. The diaphragm 21 isolates the oxygen flowing in the anode flow path 24 from the hydrogen flowing in the cathode flow path 25.

[0022] Furthermore, the water electrolyzer group 20 is not limited to being constructed by stacking multiple water electrolyzers 30; it can also be constructed by a single water electrolyzer 30. Alternatively, the water electrolyzer group 20 can be constructed by connecting multiple water electrolyzers 30 in parallel.

[0023] The anode current collector 22 is connected to the anode of the power supply unit 11, and the cathode current collector 23 is connected to the cathode of the power supply unit 11. If power is supplied by the power supply unit 11, direct current flows through each water electrolysis cell 30 of the water electrolysis cell group 20 to carry out the electrolysis reaction.

[0024] like Figure 1 As shown, water tank 2 stores the anode electrode 31 supplied to the water electrolysis cell assembly 20 (see reference). Figure 2 Water from water tank 2 is supplied to water inlet manifold 5 via supply pump 3 and gas-liquid separator 4.

[0025] Water inlet manifold 5 distributes water supplied from gas-liquid separator 4 to the anode flow path 24 of each diaphragm 21 (see reference). Figure 2 The system is configured in a manner that allows oxygenated water discharged from each anode flow path 24 to be collected together through the water outlet manifold 6 and supplied to the gas-liquid separator 4 via the circulation pump 7.

[0026] The gas-liquid separator 4 separates oxygen and water from oxygen-containing water. The separated oxygen is discharged to the outside. The separated water, along with the water supplied from the water tank 2, is supplied to the water inlet manifold 5.

[0027] The hydrogen manifold 8 will draw water from the cathode path 25 of each diaphragm 21 (see reference). Figure 2 The discharged hydrogen gas is collected and supplied to the hydrogen-liquid separator 9. Water is discharged not only from the cathode flow path 25, so the hydrogen gas supplied to the hydrogen-liquid separator 9 contains water.

[0028] Hydrogen-liquid separator 9 separates hydrogen and water. The separated water is discharged to the outside. The separated hydrogen is supplied to dehumidifier 10.

[0029] The dehumidifier 10 removes water vapor from the hydrogen gas discharged from the hydrogen-liquid separator 9. The water vapor-free hydrogen gas is then supplied to the hydrogen consumption device. Examples of hydrogen consumption devices include fuel cells.

[0030] The power supply unit 11 supplies power to the aforementioned anode current collector 22 (see reference). Figure 2 The system supplies power to the supply pump 3, gas-liquid separator 4, circulation pump 7, hydrogen-liquid separator 9, and dehumidifier 10. The control unit 12 controls the supply pump 3, gas-liquid separator 4, circulation pump 7, hydrogen-liquid separator 9, and dehumidifier 10 to optimize the operation of the water electrolysis device 1.

[0031] use Figure 3 The details of the water electrolysis cell 30 are explained below.

[0032] The anode electrode 31 includes an anode catalyst layer 34 and an anode diffusion layer 35. The anode catalyst layer 34 is in contact with the electrolyte membrane 33. The anode diffusion layer 35 is in contact with the diaphragm 21, allowing water supplied from the anode flow path 24 formed on the diaphragm 21 to diffuse. The anode diffusion layer 35 is bonded to the anode catalyst layer 34.

[0033] The anode catalyst layer 34 has a stacked structure consisting of nanosheet-shaped anode catalyst sheets 34a stacked with gaps 34b between them. That is, the anode catalyst layer 34 comprises multiple anode catalyst sheets 34a, with gaps 34b formed between adjacent anode catalyst sheets 34a. Water flowing from the water inlet manifold 5 into the anode flow path 24 is immersed in the gaps 34b of the anode catalyst layer 34, and hydrogen ions (H+) are generated from water (H2O) as protons through the reaction shown in equation (1). + The generated oxygen (O2) flows together with unreacted water in the anode flow path 24 and is discharged into the aforementioned water outlet manifold 6. The generated hydrogen ions move through the electrolyte membrane 33 to the cathode electrode 32.

[0034] 2H₂O→2H + +2e - +O2 (1)

[0035] The anode catalyst sheet 34a is a sheet in which the catalyst material is formed into a nanosheet. Two adjacent anode catalyst sheets 34a are locally integrated. This allows the laminated structure to be maintained while ensuring proton conductivity. The anode catalyst layer 34 can also have a supportless structure. "Supportless" means that no support is used; the anode catalyst layer 34 has a supportless laminated structure. The anode catalyst sheet 34a can also be a porous sheet. This improves proton conductivity.

[0036] The thickness of the anode catalyst layer 34 can be, for example, 10 nm or more and 2000 nm or less. By making the thickness of the anode catalyst layer 34 10 nm or more, the layered structure can be maintained. By making the thickness of the anode catalyst layer 34 2000 nm or less, proton conductivity can be maintained.

[0037] The anode catalyst sheet 34a contains iridium (Ir). The anode catalyst sheet 34a may also be formed of iridium oxide. The anode diffusion layer 35 may also be formed, for example, of carbon paper or titanium nonwoven fabric.

[0038] The cathode electrode 32 includes a cathode catalyst layer 36 and a cathode diffusion layer 37. The cathode catalyst layer 36 is in contact with the electrolyte membrane 33. The cathode diffusion layer 37 is in contact with the diaphragm 21. Hydrogen gas generated by the electrolysis reaction is discharged from the cathode flow path 25 formed in the diaphragm 21.

[0039] The cathode catalyst layer 36 has a stacked structure consisting of nanosheet-shaped cathode catalyst sheets 36a stacked with gaps 36b between them. That is, the cathode catalyst layer 36 comprises multiple cathode catalyst sheets 36a, with gaps 36b formed between adjacent cathode catalyst sheets 36a. In the cathode electrode 32, hydrogen ions moving from the anode electrode 31 generate hydrogen gas (H2) through the reaction shown in equation (2). The generated hydrogen gas flows in the cathode flow path 25 and is discharged into the aforementioned hydrogen manifold 8.

[0040] 2H + +2e - →H2 (2)

[0041] like Figure 3 As shown, the cathode catalyst sheet 36a is a sheet in which the catalyst material is formed into a nanosheet. Two adjacent cathode catalyst sheets 36a can also be locally integrated. This allows the laminated structure to be maintained while ensuring proton conductivity. The cathode catalyst layer 36 can also have a carrier-free structure, similar to the anode catalyst layer 34. The cathode catalyst sheet 36a can also be a porous sheet. This improves proton conductivity.

[0042] The thickness of the cathode catalyst layer 36 can be, for example, 10 nm or more and 2000 nm or less. By making the thickness of the cathode catalyst layer 36 10 nm or more, the layered structure can be maintained. By making the thickness of the cathode catalyst layer 36 2000 nm or less, proton conductivity can be maintained.

[0043] The cathode catalyst sheet 36a contains platinum (Pt). The cathode diffusion layer 37 may also be formed, for example, from carbon paper or titanium nonwoven fabric.

[0044] An electrolyte membrane 33 is disposed between the anode electrode 31 and the cathode electrode 32, and is sandwiched between the anode electrode 31 and the cathode electrode 32. The electrolyte membrane 33 can be a solid polymer electrolyte membrane (PEM). The electrolyte membrane 33 is composed of a hydrocarbon-based material. The hydrocarbon-based material can also be a material whose main chain backbone does not contain fluorine and has a heat-resistant main chain backbone. As a hydrocarbon-based material, polymers with functional groups such as sulfonic acid groups, carboxylic acid groups, phosphonic acid groups, hypophosphonic acid groups, thioimide groups, and phenolic hydroxyl groups can be used. Specific examples of hydrocarbon-based materials include polyarylene, polyetheretherketone, polyethersulfone, polyphenylene sulfide, polyimide, and polybenzoxazole polymers with sulfonated aromatic rings in the main chain. The thickness of the electrolyte membrane 33 composed of a hydrocarbon-based material can be 10 μm or more and 150 μm or less, or 13 μm or more and 40 μm or less.

[0045] Next, the manufacturing method of the water electrolysis cell 30 of this embodiment, which includes such a configuration, will be described.

[0046] First, prepare the aforementioned anode electrode 31, cathode electrode 32, and electrolyte membrane 33.

[0047] The method for fabricating the anode electrode 31 will be described. First, an iridium-containing anode catalyst sheet 34a and a pore-forming material sheet made of a pore-forming material are alternately stacked on a support by sputtering. The pore-forming material can be a metallic material that can be dissolved in an acidic solution. Then, the pore-forming material sheet is dissolved and removed using an acidic solution (an example of a removing agent). This yields an anode catalyst layer 34 with a stacked structure in which gaps 34b are formed between adjacent anode catalyst sheets 34a, and the anode catalyst sheets 34a are stacked with gaps 34b between them. The pore-forming material can also be a metallic material that can be dissolved in an alkaline solution; in this case, an alkaline solution, an example of a removing agent, is used to dissolve the pore-forming material sheet.

[0048] The method for fabricating the cathode electrode 32 will be described. First, on a support different from the support for the anode electrode 31, a cathode catalyst sheet 36a containing platinum and a pore-forming material sheet made of a pore-forming material are alternately stacked by sputtering. The pore-forming material can be a metallic material that can be dissolved in an acidic solution. Then, the pore-forming material sheet is dissolved and removed using an acidic solution (an example of a removing agent). This yields a cathode catalyst layer 36 with a stacked structure in which gaps 36b are formed between adjacent cathode catalyst sheets 36a, and the cathode catalyst sheets 36a are stacked with gaps 36b between them. The pore-forming material can also be a metallic material that can be dissolved in an alkaline solution; in this case, an alkaline solution, an example of a removing agent, is used to dissolve the pore-forming material sheet.

[0049] Next, an electrolyte membrane 33 is disposed between the anode electrode 31 and the cathode electrode 32, and the anode electrode 31 and the cathode electrode 32 are bonded to the electrolyte membrane 33.

[0050] More specifically, the anode catalyst layer 34 formed on the support is bonded to the electrolyte membrane 33. This is achieved by heating and pressurizing the anode catalyst layer 34 onto the electrolyte membrane 33. When the support functions as the anode diffusion layer 35, it is not peeled off from the anode catalyst layer 34. Alternatively, the support can be peeled off from the anode catalyst layer 34 if it is not intended to function as the anode diffusion layer.

[0051] Similarly, the cathode catalyst layer 36 formed on another support is bonded to the electrolyte membrane 33. At this time, the cathode catalyst layer 36 is bonded to the electrolyte membrane 33 by heating and pressurizing. If the support functions as a cathode diffusion layer 37, it is not peeled off from the cathode catalyst layer 36. Alternatively, if the support does not function as a cathode diffusion layer, it can be peeled off from the cathode catalyst layer 36. Furthermore, after bonding the cathode catalyst layer 36 to the electrolyte membrane 33, the anode catalyst layer 34 can also be bonded to the electrolyte membrane 33.

[0052] Thus, the water electrolysis cell 30 of this embodiment can be obtained.

[0053] According to this embodiment, the anode electrode 31 comprises an anode catalyst layer 34 formed by stacking anode catalyst sheets 34a containing iridium and formed in nanosheet form with gaps 34b. The cathode electrode 32 comprises a cathode catalyst layer 36 formed by stacking cathode catalyst sheets 36a containing platinum and formed in nanosheet form with gaps 36b. The electrolyte membrane 33 disposed between the anode electrode 31 and the cathode electrode 32 contains a hydrocarbon-based material. The hydrocarbon-based material has proton conductivity, thus promoting the movement of hydrogen ions generated in the anode electrode 31 to the cathode electrode 32. Therefore, an electrolyte membrane 33 that maintains proton conductivity without containing organic fluorine compounds can be obtained.

[0054] Furthermore, according to this embodiment, the anode electrode 31 includes an anode catalyst layer 34 formed by stacking anode catalyst sheets 34a containing iridium and formed in a nanosheet shape with gaps 34b. This increases the reaction area of ​​water. In this case, it is not necessary to include organic fluorine compounds for improving proton conductivity in the anode catalyst layer 34. Therefore, an anode electrode 31 that can promote the reaction of water without containing organic fluorine compounds can be obtained. Furthermore, since the reaction area of ​​water can be increased, the amount of catalyst material, i.e., iridium, used can be reduced. Therefore, the manufacturing cost of the anode electrode 31 can be reduced.

[0055] Furthermore, according to this embodiment, the cathode electrode 32 comprises a cathode catalyst layer 36 formed by stacking cathode catalyst sheets 36a containing platinum and formed in a nanosheet shape with gaps 36b. This increases the reaction area for hydrogen ions. In this case, it is not necessary to include organic fluorine compounds for improving proton conductivity in the cathode catalyst layer 36. Therefore, a cathode electrode 32 that promotes the reaction of hydrogen ions without containing organic fluorine compounds can be obtained. Furthermore, since the reaction area for hydrogen ions can be increased, the amount of catalyst material, i.e., platinum, used can be reduced. Therefore, the manufacturing cost of the cathode electrode 32 can be reduced.

[0056] Thus, according to this embodiment, a water electrolyzer 30 that maintains proton conductivity without containing organofluorine compounds can be provided. Furthermore, since it does not contain organofluorine compounds, precious metals can be easily separated by dissolving the water electrolyzer 30 during recycling. Therefore, the recyclability of the water electrolyzer 30 can be improved.

[0057] According to the embodiments described above, proton conductivity can be maintained without containing organic fluorine compounds.

[0058] Several embodiments of the present invention have been described, but these embodiments are given by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the scope of the invention as described in the claims and its equivalents. Furthermore, these embodiments can, of course, be suitably combined in part within the spirit of the invention.

[0059] Symbol Explanation

[0060] 1: Water electrolysis device; 20: Water electrolysis cell group; 30: Water electrolysis cell; 31: Anode electrode; 32: Cathode electrode; 33: Electrolyte membrane; 34: Anode catalyst layer; 34a: Anode catalyst sheet; 34b: Gap; 35: Anode diffusion layer; 36: Cathode catalyst layer; 36a: Cathode catalyst sheet; 36b: Gap.

Claims

1. A water electrolysis cell, comprising: An anode electrode comprising an anode catalyst layer formed by stacking iridium-containing anode catalyst sheets in nanosheet form with gaps between them; A cathode electrode comprising a cathode catalyst layer formed by stacking cathode catalyst sheets containing platinum and formed in nanosheet form with gaps between them; and An electrolyte membrane, disposed between the anode electrode and the cathode electrode, contains a hydrocarbon-based material.

2. A water electrolysis cell assembly comprising the water electrolysis cell as described in claim 1.

3. A method for manufacturing a water electrolyzer, comprising the following steps: The process of preparing an anode electrode, wherein the anode electrode comprises an anode catalyst layer formed by stacking anode catalyst sheets containing iridium and formed in nanosheet form with gaps between them; The process of preparing a cathode electrode, wherein the cathode electrode comprises a cathode catalyst layer formed by stacking cathode catalyst sheets containing platinum and formed in nanosheet form with gaps between them; The process of preparing an electrolyte membrane containing hydrocarbon materials; and The process of placing the electrolyte membrane between the anode electrode and the cathode electrode, and simultaneously bonding the anode electrode and the cathode electrode to the electrolyte membrane.

4. The method for manufacturing a water electrolysis cell according to claim 3, wherein, In the process of preparing the anode electrode, the anode electrode is prepared by alternately stacking the anode catalyst sheet and the pore-forming material sheet made of pore-forming material, and removing the pore-forming material sheet with a removal agent.

5. The method for manufacturing a water electrolysis cell according to claim 4, wherein, The anode catalyst sheet and the pore-forming material sheet are formed by sputtering.

6. The method for manufacturing a water electrolyzer according to claim 3, wherein, In the process of preparing the cathode electrode, the cathode electrode is prepared by alternately stacking the cathode catalyst sheet and the pore-forming material sheet made of pore-forming material, and removing the pore-forming material sheet with a removal agent.

7. The method for manufacturing a water electrolysis cell according to claim 6, wherein, The cathode catalyst sheet and the pore-forming material sheet are formed by sputtering.

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