Water electrolysis cell, water electrolysis cell stack and method of producing water electrolysis cell

Abstract

To provide a water electrolysis cell capable of holding proton conductivity without containing an organic fluorine compound.SOLUTION: The water electrolysis cell according to an embodiment of the present invention contains an anode electrode including an anode catalyst layer formed of nanosheet-shaped anode catalyst sheets containing iridium oxide, laminated one after another with a gap therebetween, a cathode electrode including a cathode catalyst layer formed of nanosheet-shaped cathode catalyst sheets containing platinum, laminated one after another with a gap therebetween, and an electrolyte membrane disposed between the anode electrode and the cathode electrode to contain a hydrocarbon-based material.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The embodiments relate to a water electrolysis cell, a water electrolysis cell stack, and a method for manufacturing a water electrolysis cell. [Background technology]

[0002] In recent years, electrochemical cells have been actively researched. For example, polymer electrolyte membrane electrolysis cells (PEMEC) are expected to be used for hydrogen generation in large-scale energy storage systems.

[0003] When a water electrolysis device using a water electrolysis cell is in operation, a direct current is passed through the water electrolysis cell, electrolyzing water supplied to the anode electrode. At the anode electrode, protons (hydrogen ions) are produced by a hydrogen oxidation reaction. The protons then pass through the electrolyte membrane to the cathode electrode, where hydrogen is produced by a hydrogen reduction reaction.

[0004] Water electrolysis cells are equipped with a catalyst layer to promote the electrolysis reaction. Perfluorosulfonic acid is generally used as an ionomer in the catalyst layer and electrolyte membrane to improve proton conductivity. Perfluorosulfonic acid belongs to the group of fluorocarbons (PFAS), which are being increasingly restricted due to their harmful effects on both the environment and humans. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 159820 [Patent Document 2] Japanese Patent Application Publication No. 2019-057443 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the embodiments is to provide a water electrolysis cell, a water electrolysis cell stack, and a method for manufacturing a water electrolysis cell that can maintain proton conductivity without containing an organic fluorine compound. [Means for solving the problem]

[0007] A water electrolysis cell according to an embodiment includes an anode electrode including an anode catalyst layer in which anode catalyst sheets each containing iridium oxide and formed into a nanosheet shape are laminated with gaps therebetween; a cathode electrode including a cathode catalyst layer in which cathode catalyst sheets each containing platinum and formed into a nanosheet shape are laminated with gaps therebetween; and an electrolyte membrane containing a hydrocarbon-based material, which is disposed between the anode electrode and the cathode electrode.

[0008] The water electrolysis cell stack according to the embodiment includes the water electrolysis cell described above.

[0009] A method for manufacturing a water electrolysis cell according to an embodiment includes the steps of: preparing an anode electrode including an anode catalyst layer in which anode catalyst sheets each formed into a nanosheet containing iridium oxide are laminated with a gap therebetween; preparing a cathode electrode including a cathode catalyst layer in which cathode catalyst sheets each formed into a nanosheet containing platinum are laminated with a gap therebetween; preparing an electrolyte membrane containing a hydrocarbon-based material; and disposing the electrolyte membrane between the anode electrode and the cathode electrode, and joining the anode electrode and the cathode electrode to the electrolyte membrane. [Effects of the Invention]

[0010] According to the embodiment, proton conductivity can be maintained without containing an organic fluorine compound. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing an example of a water electrolysis apparatus according to the present embodiment. [Figure 2]FIG. 2 is a diagram showing a schematic configuration of the water electrolysis cell stack shown in FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view showing the general configuration of the water electrolysis cell shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a water electrolysis cell, a water electrolysis cell stack, and a method for manufacturing a water electrolysis cell according to this embodiment will be described with reference to the drawings.

[0013] First, an example of a water electrolysis device to which the water electrolysis cell stack according to the present embodiment is applied will be described with reference to FIG.

[0014] 1 , the water electrolysis apparatus 1 is an example of an apparatus that generates hydrogen and oxygen using an electrolyte membrane 33 described below. The water electrolysis apparatus 1 includes a water electrolysis cell stack 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.

[0015] 2, the water electrolysis cell stack 20 is configured by stacking a plurality of water electrolysis cells 30. More specifically, the water electrolysis cell stack 20 includes a plurality of water electrolysis cells 30, a plurality of separators 21, anode current collectors 22, and cathode current collectors 23. The water electrolysis cells 30, separators 21, anode current collectors 22, and cathode current collectors 23 are clamped and pressed by a pair of clamping plates (not shown).

[0016] The water electrolysis cell 30 includes an anode electrode 31, a cathode electrode 32, and an electrolyte membrane 33. The water electrolysis cell 30 is also called a membrane electrode assembly.

[0017] As shown in FIG. 2, the separator 21 is interposed between two water electrolysis cells 30. An anode flow path 24 is formed on the surface of the separator 21 that contacts the anode electrode 31. The anode flow path 24 may be composed of a plurality of grooves. A cathode flow path 25 is formed on the surface of the separator 21 that contacts the cathode electrode 32. The cathode flow path 25 may be composed of a plurality of grooves. The separator 21 is electrically conductive and gas impermeable. The separator 21 separates oxygen gas flowing through the anode flow path 24 from hydrogen gas flowing through the cathode flow path 25.

[0018] The water electrolysis cell stack 20 is not limited to being configured by stacking a plurality of water electrolysis cells 30, but may be configured by a single water electrolysis cell 30. Alternatively, the water electrolysis cell stack 20 may be configured by connecting a plurality of water electrolysis cells 30 in parallel.

[0019] The anode current collector 22 is connected to the positive electrode of the power supply unit 11, and the cathode current collector 23 is connected to the negative electrode of the power supply unit 11. When power is supplied from the power supply unit 11, a direct current flows through each water electrolysis cell 30 in the water electrolysis cell stack 20, causing an electrolytic reaction.

[0020] As shown in Figure 1, the water tank 2 stores water to be supplied to the anode electrode 31 (see Figure 2) of the water electrolysis cell stack 20. The water in the water tank 2 is supplied by a supply pump 3 to a water inlet manifold 5 through a gas-liquid separator 4.

[0021] The water inlet manifold 5 is configured to distribute the water supplied from the gas-liquid separator 4 to the anode flow paths 24 (see FIG. 2) of each separator 21. The water containing oxygen gas discharged from each anode flow path 24 is collected in the water outlet manifold 6 and supplied to the gas-liquid separator 4 by the circulation pump 7.

[0022] The gas-liquid separator 4 separates the oxygen gas and water from the water containing oxygen gas. The separated oxygen gas is discharged to the outside. The separated water is supplied to the water inlet manifold 5 together with the water supplied from the water tank 2.

[0023] The hydrogen manifold 8 collects hydrogen gas discharged from the cathode flow paths 25 (see FIG. 2) of each separator 21 and supplies it to the hydrogen-gas-liquid separator 9. Since not only hydrogen gas but also water is discharged from the cathode flow paths 25, the hydrogen gas supplied to the hydrogen-gas-liquid separator 9 contains water.

[0024] The hydrogen gas-liquid separator 9 separates the hydrogen gas from the water. The separated water is discharged to the outside. The separated hydrogen gas is supplied to the dehumidifier 10.

[0025] The dehumidifier 10 removes water vapor from the hydrogen gas discharged from the hydrogen gas-liquid separator 9. The hydrogen gas from which the water vapor has been removed is supplied to a hydrogen consuming device. An example of the hydrogen consuming device is a fuel cell.

[0026] The power supply unit 11 supplies power to the above-described anode current collector 22 (see FIG. 2 ) and cathode current collector 23. The control unit 12 controls the supply pump 3, the gas-liquid separator 4, the circulation pump 7, the hydrogen gas-liquid separator 9, and the dehumidifier 10, and optimizes the operation of the water electrolysis apparatus 1.

[0027] The water electrolysis cell 30 will be described in detail with reference to FIG.

[0028] The anode electrode 31 includes an anode catalyst layer 34 and an anode diffusion layer 35. The anode catalyst layer 34 is composed of a large number of nanosheets applied to the surface of the fibers of the 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 separator 21 and diffuses water supplied from the anode flow path 24 formed in the separator 21. The anode diffusion layer 35 is bonded to the anode catalyst layer 34. The anode electrode 31 does not necessarily contain an ionomer therein.

[0029] The anode catalyst layer 34 has a laminated structure in which nanosheet-shaped anode catalyst sheets 34a are laminated with gaps 34b between them. That is, the anode catalyst layer 34 includes a plurality of anode catalyst sheets 34a, and gaps 34b are formed between two adjacent anode catalyst sheets 34a. Water flowing into the anode flow path 24 from the water inlet manifold 5 enters the gaps 34b of the anode catalyst layer 34, and water (HO) is converted into protons (H + ) and oxygen gas (O2). The generated oxygen gas flows through gap 34b to the anode flow channel 24 together with unreacted water and is discharged to the water outlet manifold 6. The generated protons move through the electrolyte membrane 33 to the cathode electrode 32. 2H2O→4H + +4e - +O2(1)

[0030] The anode catalyst sheet 34a is a sheet in which a catalyst material is formed into a nanosheet shape without using an ionomer. Two adjacent anode catalyst sheets 34a are partially integrated. This ensures proton conductivity and maintains the laminated structure. Because the anode nanosheet is thin and attached to the electrolyte membrane 33, protons can move to the electrolyte membrane 33 without using an ionomer. This improves proton conductivity.

[0031] The thickness of the anode catalyst layer 34 may 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 laminated structure can be maintained. By making the thickness of the anode catalyst layer 34 2000 nm or less, proton conductivity can be maintained.

[0032] The anode catalyst sheet 34a may be made of iridium oxide, and the anode diffusion layer 35 may be made of, for example, titanium nonwoven fabric.

[0033] 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 separator 21. Hydrogen gas produced by the electrolytic reaction is discharged from a cathode flow path 25 formed in the separator 21. The cathode electrode 32 does not necessarily contain an ionomer therein.

[0034] The cathode catalyst layer 36 has a laminated structure in which nanosheet-shaped cathode catalyst sheets 36a are stacked with gaps 36b between them. That is, the cathode catalyst layer 36 includes a plurality of cathode catalyst sheets 36a, with gaps 36b formed between two adjacent cathode catalyst sheets 36a. In the cathode electrode 32, hydrogen gas (H2) is generated from protons migrated from the anode electrode 31 by the reaction shown in formula (2) below. The generated hydrogen gas flows through the cathode flow path 25 and is discharged to the hydrogen manifold 8 described above. 2H + +2e - →H2(2)

[0035] As shown in FIG. 3, the cathode catalyst sheet 36a is a sheet in which the catalyst material is formed into a nanosheet shape without using an ionomer. Two adjacent cathode catalyst sheets 36a may be partially integrated. This allows the laminated structure to be maintained. Like the anode catalyst layer 34, the cathode nanosheet is thin and is attached to the electrolyte membrane 33, allowing the cathode catalyst layer 36 to maintain proton conductivity.

[0036] The thickness of the cathode catalyst layer 36 may 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 laminated structure can be maintained. By making the thickness of the cathode catalyst layer 36 2000 nm or less, proton conductivity can be maintained.

[0037] The cathode catalyst sheet 36a contains platinum (Pt). The cathode diffusion layer 37 may be made of, for example, carbon paper or titanium nonwoven fabric.

[0038] The electrolyte membrane 33 is disposed between the anode electrode 31 and the cathode electrode 32 and is sandwiched between them. The electrolyte membrane 33 may be a solid polymer electrolyte membrane (PEM). The electrolyte membrane 33 is made of a hydrocarbon-based material. The hydrocarbon-based material may be a material that does not contain fluorine in its main chain and has a heat-resistant main chain. The hydrocarbon-based material may be a polymer having a functional group such as a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, a phosphinic acid group, a sulfonylimide group, or a phenolic hydroxyl group. Specific examples of hydrocarbon-based materials include polyarylene-based, polyetheretherketone-based, polyethersulfone-based, polyphenylene sulfide-based, polyimide-based, or polybenzazole-based polymers in which the aromatic rings in the main chain are sulfonated. The thickness of the electrolyte membrane 33 made of a hydrocarbon-based material may be 10 μm to 150 μm, or 13 μm to 40 μm.

[0039] Next, a method for manufacturing the water electrolysis cell 30 according to this embodiment having the above-described configuration will be described.

[0040] First, the anode electrode 31, the cathode electrode 32, and the electrolyte membrane 33 described above are prepared.

[0041] The method for fabricating the anode electrode 31 will now be described. First, anode catalyst sheets 34a containing iridium oxide and sheets made of other metal materials are alternately laminated on the fibers of the diffusion layer on a support by sputtering. The metal material is removed by dissolving in an acidic solution. This creates gaps 34b between two adjacent anode catalyst sheets 34a, resulting in an anode catalyst layer 34 having a laminated structure in which the anode catalyst sheets 34a are stacked with the gaps 34b between them.

[0042] The method for fabricating the cathode electrode 32 will now be described. First, platinum-containing cathode catalyst sheets 36a and sheets made of other metal materials are alternately laminated on the fibers of the cathode diffusion layer 37 by sputtering on a support different from the support of the anode electrode 31. The metal material is soluble in an acidic solution. The metal sheets are then dissolved and removed in an acidic solution (an example of a remover). This forms a gap 36b between two adjacent cathode catalyst sheets 36a, resulting in a cathode catalyst layer 36 having a laminated structure in which the cathode catalyst sheets 36a are stacked with the gap 36b between them.

[0043] Next, the 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 joined to the electrolyte membrane 33. The anode electrode 31 and the cathode electrode 32 are attached to the electrolyte membrane 33 by hot pressing.

[0044] In this manner, the water electrolysis cell 30 according to this embodiment is obtained.

[0045] As described above, according to this embodiment, the anode 31 includes an anode catalyst layer 34 in which nanosheet-shaped anode catalyst sheets 34a containing iridium oxide are laminated with gaps 34b between them. The cathode 32 includes a cathode catalyst layer 36 in which nanosheet-shaped cathode catalyst sheets 36a containing platinum are laminated with gaps 36b between them. The electrolyte membrane 33 disposed between the anode 31 and the cathode 32 includes a hydrocarbon-based material. Because the hydrocarbon-based material has proton conductivity, it can promote the migration of protons generated at the anode 31 to the cathode 32. This allows for an electrolyte membrane 33 that can maintain proton conductivity without containing an organic fluorine compound.

[0046] Furthermore, according to this embodiment, the anode electrode 31 includes an anode catalyst layer 34 in which nanosheet-shaped anode catalyst sheets 34a containing iridium oxide are stacked with gaps 34b between them. This increases the water reaction area. In this case, it is not necessary to include an ionomer, an organic fluorine compound, in the anode catalyst layer 34 to improve proton conductivity. This makes it possible to obtain an anode electrode 31 that can promote water reaction without including an organic fluorine compound. Furthermore, because the water reaction area can be increased, the amount of iridium used as a catalyst material can be reduced. This reduces the material cost of the anode electrode 31.

[0047] Furthermore, according to this embodiment, the cathode electrode 32 includes a cathode catalyst layer 36 in which platinum-containing nanosheet-shaped cathode catalyst sheets 36a are stacked with gaps 36b between them. This increases the electrochemical reaction area of ​​the cathode catalyst for hydrogen production. In this case, it is not necessary to include an ionomer, an organic fluorine compound, in the cathode catalyst layer 36 to improve proton conductivity. This makes it possible to obtain a cathode electrode 32 that can promote hydrogen reaction without including an organic fluorine compound. Furthermore, because the electrochemical reaction area can be increased, the amount of platinum catalyst used can be reduced. This reduces the material cost of the cathode electrode 32.

[0048] As described above, according to the present embodiment, it is possible to provide a water electrolysis cell 30 that can maintain proton conductivity without containing an organic fluorine compound. Furthermore, since the water electrolysis cell 30 does not contain an organic fluorine compound, the water electrolysis cell 30 does not generate fluorine when recycled. This simplifies the recycling equipment for the water electrolysis cell 30.

[0049] According to the above-described embodiment, proton conductivity can be maintained without containing an organic fluorine compound.

[0050] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, it is of course possible to combine parts of these embodiments as appropriate within the spirit of the invention. [Explanation of symbols]

[0051] 1: water electrolysis device, 20: water electrolysis cell stack, 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. an anode electrode including an anode catalyst layer in which anode catalyst sheets formed in a nanosheet shape and containing iridium oxide are stacked with gaps between them; a cathode electrode including a cathode catalyst layer in which platinum-containing nanosheet-shaped cathode catalyst sheets are stacked with gaps between them; an electrolyte membrane containing a hydrocarbon-based material disposed between the anode electrode and the cathode electrode; A water electrolysis cell comprising:

2. A water electrolysis system comprising the water electrolysis cell according to claim 1. Water electrolysis cell stack.

3. preparing an anode electrode including an anode catalyst layer in which anode catalyst sheets formed in the form of nanosheets containing iridium oxide are stacked with gaps between them; preparing a cathode electrode including a cathode catalyst layer in which platinum-containing nanosheet-shaped cathode catalyst sheets are stacked with gaps between them; providing an electrolyte membrane containing a hydrocarbon-based material; disposing the electrolyte membrane between the anode electrode and the cathode electrode, and joining the anode electrode and the cathode electrode to the electrolyte membrane; A method for manufacturing a water electrolysis cell, comprising:

4. In the step of preparing the anode electrode, the anode catalyst sheets and metal sheets are alternately stacked, and the metal sheets are removed using a remover to prepare the anode electrode. The method for producing a water electrolysis cell according to claim 3 .

5. The anode catalyst sheet and the metal sheet are formed by sputtering. The method for producing a water electrolysis cell according to claim 4.

6. In the step of preparing the cathode electrode, the cathode catalyst sheets and metal sheets are alternately stacked, and the metal sheets are removed using a remover to prepare the cathode electrode. The method for producing a water electrolysis cell according to any one of claims 3 to 5.

7. The cathode catalyst sheet and the metal sheet are formed by sputtering. The method for producing a water electrolysis cell according to claim 6.

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