Water electrolysis cells, water electrolysis stacks

Abstract

To provide a water electrolysis cell in which the movement of a generated gas is less likely to be inhibited by water and the deterioration in water electrolysis performance is suppressed.SOLUTION: Provided is a water electrolysis cell, which is a water electrolysis cell that has an anode placed on one side and a cathode placed on the other side with a solid polymer electrolyte membrane therebetween, and in which, in the anode an anode catalyst layer, an anode gas diffusion layer, and an anode separator are laminated from the solid polymer electrolyte membrane side, in the anode separator a flow path is formed, and the flow path is formed to extend in a wave shape.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a water electrolysis cell and a water electrolysis stack used for water electrolysis. [Background technology]

[0002] For example, Patent Document 1 discloses a stack structure in which water electrolysis cells fastened with a plurality of screw shafts are stacked horizontally. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-147562 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional technology, oxygen generated at the anode (oxygen generating electrode) is not properly discharged and remains inside the anode, making it difficult to supply water for electrolysis, resulting in problems such as reduced electrolysis performance and durability.

[0005] In view of the above problems, an object of the present disclosure is to provide a water electrolysis cell in which the movement of generated gas is less likely to be hindered by water and a decrease in water electrolysis performance is suppressed. [Means for solving the problem]

[0006] The present application discloses a water electrolysis cell having an anode disposed on one side of a solid polymer electrolyte membrane and a cathode disposed on the other side thereof, wherein the anode is formed by laminating, from the solid polymer electrolyte membrane side, an anode catalyst layer, an anode gas diffusion layer, and an anode separator, and the anode separator has a flow path formed therein, the flow path being formed so as to extend in a wavy pattern.

[0007] In the water electrolysis cell, the inner surface of the flow channel of the anode separator may be subjected to a water-repellent treatment.

[0008] In the water electrolysis cell, the surface of the anode gas diffusion layer facing the anode separator may be subjected to a hydrophilic treatment.

[0009] The present application discloses a water electrolysis stack in which the above-described water electrolysis cells are stacked, and the water electrolysis cells are arranged so that the flow paths extend vertically, with the inlet at the bottom and the outlet at the top. [Effects of the Invention]

[0010] According to the present disclosure, in a water electrolysis cell, the movement of generated gas is less likely to be hindered by water, and a decrease in water electrolysis performance can be suppressed. [Brief explanation of the drawings]

[0011] [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 of the water electrolysis section 10a of the water electrolysis cell 10. [Figure 3] FIG. 3 is a perspective view of the appearance of a portion of the anode separator 14. As shown in FIG. [Figure 4] FIG. 4 is a cross section of a portion of the anode separator 14. [Figure 5] FIG. 5 is a diagram illustrating the structure of the water electrolysis stack 20. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1. Water electrolysis cell configuration Figures 1 and 2 illustrate 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, and Figure 2 is a partial cross-sectional view taken along the line A-A in Figure 1, illustrating the layer structure of the water electrolysis section 10a, which is the portion of the water electrolysis cell 10 where water electrolysis takes place.

[0013] The water electrolysis cell 10 is composed of multiple layers, one of which serves as an oxygen evolution electrode (anode) and the other as a hydrogen evolution electrode (cathode) sandwiching a solid polymer electrolyte membrane 11. 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. 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 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 cell 10 in the water electrolysis unit 10a is typically about 1.3 mm. The layers are, for example, as follows:

[0014] 1.1.Solid polymer electrolyte membrane The solid polymer electrolyte membrane 11 is one embodiment of a 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 100 μm or less, preferably 50 μm or less, and more preferably 30 μm or less.

[0015] 1.2.Anode catalyst layer The anode catalyst layer (oxygen electrode catalyst layer) 12 is a layer containing a catalyst containing at least one of a noble metal catalyst such as Pt, Ru, Ir, etc. and an oxide thereof. 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.

[0016] 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.

[0017] 1.3.Anode gas diffusion layer The anode gas diffusion layer 13 may be made of a known material, such as a porous conductive material made of a sintered body of metal fibers (e.g., titanium fibers) or metal particles (titanium particles). Furthermore, in this embodiment, the surface 13a of the anode gas diffusion layer 13 facing the flow path 14a of the anode separator 14 may be subjected to a hydrophilic treatment. This makes it easier for water to collect on the surface of the anode gas diffusion layer 13, and by collecting and guiding the water, it becomes easier to introduce water into the anode gas diffusion layer 13, enabling smooth water splitting. The hydrophilic property is preferably such that the contact angle is 50 degrees or less in a wettability test using ion-exchanged water. Examples of hydrophilic treatment include UV treatment, plasma treatment, etc. to impart hydrophilicity to the surface 13a of the anode gas diffusion layer 13 itself, and spraying an inorganic compound such as silica or a hydrophilic resin onto the surface 13a to form a hydrophilic layer. However, although a layer of a hydrophilic material may be formed as a hydrophilic treatment, the layer should not be formed on the surface that comes into contact with the anode separator 14. This is because if a hydrophilic material exists at the interface with the anode separator, it will act as a resistor.

[0018] 1.4.Anode Separator The anode separator 14 is a member that supplies pure water to the anode gas diffusion layer 13 and has a flow path 14a through which oxygen generated by decomposition of the water flows. Figures 3 and 4 illustrate the configuration of the flow channels in the water electrolysis unit 10a of the anode separator 14. Figures 3 and 4 are conceptual schematic diagrams for explanation, and in reality, the structure is finer and many more flow channels are arranged. Figure 3 is an external perspective view of the portion of the anode separator 14 that is arranged in the water electrolysis unit 10a, and Figure 4 is a cross-sectional view taken along the line CC in Figure 3.

[0019] As can be seen from Fig. 4, the flow paths 14a of the anode separator 14 are formed in a wavy shape. This makes it possible to turbulently flow the water flowing through the flow paths 14a, making it easier to supply the water to the anode gas diffusion layer 13. The shape of the waves is not particularly limited, and in addition to the triangular wave shown in Fig. 4, they may be sinusoidal waves, rectangular waves, or other irregular waves. Furthermore, the wave shape preferably has a large amplitude and a short wavelength so that the pressure loss during water delivery is within the capacity of the liquid delivery pump, etc. More specifically, the amplitude is preferably at least twice the width of the flow path (the size of the flow path in the direction in which the multiple flow paths are arranged), and the wavelength is preferably no more than 10 times the width of the flow path.

[0020] In this embodiment, the bottom surface 14b and side surface 14c (see FIG. 2), which are the inner surfaces of the flow channels 14a of the anode separator 14, are treated to be water-repellent. This allows water to be repelled from the inner surfaces of the flow channels 14a and guided to the anode gas diffusion layer 13. The degree of water repellency is not particularly limited, but in a water repellency test using ion-exchanged water, the sliding angle should be 70 degrees or less, and preferably 10 degrees or less. The specific form of the water-repellent treatment is not particularly limited, but it can be performed by forming a water-repellent layer by spraying a water-repellent material such as Teflon (registered trademark), etc. In this embodiment, the bottom surface 14b and the side surface 14c of the flow channel 14a are made water-repellent, but it is also possible to make only the bottom surface 14a water-repellent.

[0021] As can be seen from FIG. 1, the anode separator 14 has a water inlet hole HO at a position extending outward from the water electrolysis unit 10a and at one end of the flow path 14a. in1 , water inlet hole H2O in2 At the other end of the flow path 14a, a water and oxygen outlet hole O2 / H2O out , water and hydrogen outlet hole H2 / H2O out Here, one end of the flow path 14a is provided with a water inlet hole H2O in1 The other end is connected to the water and oxygen outlet port O2 / H2O out It leads to.

[0022] 1.5. Cathode catalyst layer The catalyst contained in the cathode catalyst layer 15 can be a known catalyst, and examples thereof include platinum, platinum-coated titanium, platinum-supported carbon, palladium-supported carbon, cobalt glyoxime, and nickel glyoxime. 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.

[0023] 1.6. Cathode gas diffusion layer The cathode gas diffusion layer 16 may be made of a known material, such as a porous material having gas permeability and electrical conductivity, such as carbon cloth or carbon paper.

[0024] 1.7. Cathode Separator The cathode separator 17 is a member having a flow path 17a through which hydrogen generated by the reduction of hydrogen ions and water accompanying the hydrogen ions when they permeate the solid polymer electrolyte membrane 11 flow. The bottom surface 17b and side surface 17c, which are the inner surfaces of the flow channel 17, may be subjected to a hydrophilic treatment. This allows water to be guided to the bottom surface 17b of the flow channel 17a, and hydrogen is concentrated on the cathode gas diffusion layer 16 side of the flow channel 17a, allowing hydrogen gas to smoothly flow from the cathode gas diffusion layer 16 to the flow channel 17a. The degree of hydrophilicity is not particularly limited, but it is preferable that the contact angle be 50 degrees or less in a wettability test using ion-exchanged water. The hydrophilic treatment is not particularly limited, but may be performed by forming a hydrophilic layer by spraying an inorganic compound such as silica or a hydrophilic resin, or by UV treatment or plasma treatment to impart hydrophilicity to the inner surface of the flow channel 17a itself. In this embodiment, the bottom surface 17b and the side surface 17c of the flow channel 17a are made hydrophilic, but it is also possible to impart hydrophilicity to only the bottom surface 17b.

[0025] As can be seen from FIG. 1, the cathode separator 17 has a water inlet hole HO at a position extending outward from the water electrolysis unit 10a and at a position on one end side of the flow path 17a. in1 , water inlet hole H2O in2 At the other end of the flow path 17a, a water and oxygen outlet hole O2 / H2O out , water and hydrogen outlet hole H2 / H2O out Here, one end of the flow path 17a is provided with a water inlet hole H2O in2 The other end is connected to the water and hydrogen outlet port H2 / H2O out It leads to.

[0026] 1.8. Hydrogen generation using water electrolysis cells The water electrolysis cell 10 described above generates hydrogen and oxygen from pure water as follows: Therefore, the water electrolysis cell and water electrolysis stack of the present disclosure may include known components and configurations necessary for generating hydrogen in addition to those described above. Pure water (HO) supplied to the anode (oxygen generating electrode) from the flow path 14a of the anode separator 14 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). The generated hydrogen reaches the cathode separator 17 and is discharged from the flow path 17a. Incidentally, the oxygen generated in the anode catalyst layer 12 reaches the anode separator 14 and is discharged from the flow path 14a.

[0027] 2. Water electrolysis stack The water electrolysis stack 20 is a component formed by stacking a plurality of (approximately 50 to 400) of the above-described water electrolysis cells 10, and generates hydrogen and oxygen by passing electricity through the plurality of water electrolysis cells 10. An outline of the configuration is shown in Figure 5. The water electrolysis stack 20 includes a stack case 21, end plates 22, a plurality of water electrolysis cells 10, and a biasing member 23.

[0028] The stack case 21 is a housing that houses a plurality of stacked water electrolysis cells 10 and the biasing member 23. In this embodiment, the stack case 21 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 21a.

[0029] The end plate 22 is a plate-shaped member that closes the opening of the stack case 21. The end plate 22 is fixed to the stack case 21 with bolts, nuts, etc. at the portion where it overlaps with the flange 21a of the stack case 21 so as to cover the stack case 21.

[0030] 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. 5, the water electrolysis cells 10 are stacked horizontally, and in each water electrolysis cell 10, the H2O in1 Water is supplied to the anode separator 14 from the anode separator 14, and the water and generated oxygen flow from the bottom to the top as shown by the straight arrows in FIGS. 1 and 4. out is emitted from

[0031] The biasing member 23 is housed inside the stack case 21 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.

[0032] 3. Effects etc. As described above, the water electrolysis cell 10 produces hydrogen and oxygen. When the water for electrolysis supplied to the anode separator 14 flows through the flow path 14a, it collides with the wall of the flow path 14a and becomes turbulent, facilitating the flow to be supplied to the anode gas diffusion layer 13. In addition, the generated oxygen moves without remaining in place and is smoothly discharged. This improves electrolysis performance, prevents the solid polymer electrolyte membrane 11 from drying out, and improves durability.

[0033] In particular, when the water electrolysis cell 10 is arranged in the water electrolysis stack 20 as described above, if water is supplied from below and flows upward, the water is likely to accumulate at the bottom due to the influence of gravity, which reduces the electrolysis performance. However, as disclosed herein, the above-described effect of the flow path 14a can suppress the reduction in electrolysis performance. [Explanation of symbols]

[0034] 10 Water electrolysis cell 11 Solid polymer electrolyte membrane 12 Anode catalyst layer 13 Anode gas diffusion layer (oxygen evolution electrode gas diffusion layer) 14 Anode separator (oxygen evolution electrode separator) 15 Cathode catalyst layer 16 Cathode gas diffusion layer (hydrogen evolution electrode gas diffusion layer) 17 Cathode separator (hydrogen evolution electrode separator) 20 Water electrolysis stack

Claims

1. A water electrolysis cell having an anode disposed on one side of a solid polymer electrolyte membrane and a cathode disposed on the other side thereof, the anode is provided with an anode catalyst layer, an anode gas diffusion layer, and an anode separator laminated on the anode from the solid polymer electrolyte membrane side; a flow path is formed in the anode separator, and the flow path is formed to extend in a wavy shape; The wave shape has an amplitude that is at least twice the width of the flow path and a wavelength that is not more than 10 times the width of the flow path, and is a shape that causes turbulent water flow in the area disposed on the anode gas diffusion layer. water electrolysis cell.

2. 2. The water electrolysis cell according to claim 1, wherein an inner surface of the flow path of the anode separator is subjected to a water-repellent treatment.

3. 3. The water electrolysis cell according to claim 1, wherein a surface of the anode gas diffusion layer facing the anode separator is subjected to a hydrophilic treatment.

4. A water electrolysis stack comprising a stack of water electrolysis cells according to any one of claims 1 to 3, a water electrolysis stack, wherein the water electrolysis cells are arranged such that the flow paths extend in a vertical direction, with an inlet at the bottom and an outlet at the top.

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