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 cathode a cathode catalyst layer, a cathode gas diffusion layer, and a cathode separator are laminated from the solid polymer electrolyte membrane side, in the anode separator a flow path is formed, on the wall surface of the anode separator flow path water repellency is imparted, in the cathode a flow path is formed, and on the wall surface of the flow path of the cathode separator hydrophilicity is imparted.SELECTED DRAWING: Figure 3

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 water electrolysis stack in which water electrolysis cells fastened with a plurality of screw shafts are stacked vertically with the anodes on top and the cathodes on the bottom. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-189689 Summary of the Invention [Problem to be solved by the invention]

[0004] At the anode (oxygen generation electrode), supplied water is efficiently supplied to the anode gas diffusion layer (oxygen electrode gas diffusion layer), and at the cathode (hydrogen generation electrode), generated hydrogen is efficiently extracted and recovered from the cathode, thereby achieving high electrolysis performance. However, oxygen generated at the anode can inhibit the movement of water, while water that accompanies hydrogen ions and permeates the electrolyte membrane (produced water) at the cathode can inhibit the movement of hydrogen, hindering the improvement of water electrolysis performance.

[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 comprises an anode catalyst layer, an anode gas diffusion layer, and an anode separator laminated from the solid polymer electrolyte membrane side, the cathode comprises a cathode catalyst layer, a cathode gas diffusion layer, and a cathode separator laminated from the solid polymer electrolyte membrane side, a flow path is formed in the anode separator, and the wall surfaces of the flow path in the anode separator are made water-repellent, and the cathode separator comprises a flow path, and the wall surfaces of the flow path in the cathode separator are made hydrophilic.

[0007] In the water electrolysis cell, a portion of the anode gas diffusion layer facing the flow path of the anode separator may be subjected to a hydrophilic treatment.

[0008] The present application also discloses a water electrolysis stack including a plurality of the water electrolysis cells stacked in a vertical direction, with the anodes positioned on top and the cathodes positioned on the bottom. [Effects of the Invention]

[0009] According to the present disclosure, gas and water can be efficiently separated in the separator, and the movement of the generated gas is less likely to be hindered by water, thereby suppressing a decrease in water electrolysis performance. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view of a water electrolysis cell 10. [Figure 2] FIG. 2 is a conceptual diagram illustrating the layer structure of the water electrolysis section 10a of the water electrolysis cell 10. [Figure 3] FIG. 3 is an enlarged view of a part of FIG. [Figure 4] FIG. 4 is a diagram illustrating the structure of the water electrolysis stack 20. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1. Water electrolysis cell configuration Figures 1 to 3 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. Figure 3 is an enlarged view of the area indicated by III in Figure 2.

[0012] 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:

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 1.3.Anode gas diffusion layer The anode gas diffusion layer 13 may be made of a known material, but is made of a material having gas permeability and conductivity. Specific examples include 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 anode gas diffusion layer 13 may be subjected to a hydrophilic treatment on its surface 13a facing the flow path 14a of the anode separator 14. 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. Here, "hydrophilic" preferably means 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 forming a hydrophilic layer on the surface 13a by spraying an inorganic compound such as silica or a hydrophilic resin, for example. 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.

[0017] 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. In this embodiment, the bottom surface 14b and side surface 14c, which are the inner surfaces of the flow path 14a of the anode separator 14, are treated to be water-repellent. This allows water to be repelled from the inner surface of the flow path 14a and guided to the anode gas diffusion layer 13. 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). In this embodiment, the bottom surface 14b and side surface 14c of the flow path 14a are made water-repellent, but it is also possible to make only the bottom surface 14a water-repellent. Here, "water-repellent" means that in a water-repellency test using ion-exchanged water, the sliding angle is 70 degrees or less, preferably 10 degrees or less.

[0018] 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 in2At 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.

[0019] 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.

[0020] 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.

[0021] 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, thereby allowing hydrogen gas to smoothly flow from the cathode gas diffusion layer 16 to the flow channel 17a. Here, "hydrophilic" preferably means that the contact angle is 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.

[0022] 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 one end 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.

[0023] 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.

[0024] 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 4. 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.

[0025] 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.

[0026] 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.

[0027] The water electrolysis cell 10 is as described above. A plurality of such water electrolysis cells 10 are stacked. In this embodiment, the water electrolysis cells 10 are stacked vertically, and each water electrolysis cell 10 is arranged with its anode (oxygen generating electrode) on top and its cathode (hydrogen generating electrode) on the bottom, as shown in Figures 2 and 3 .

[0028] 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.

[0029] 3. Effects etc. As described above, hydrogen and oxygen are produced by the water electrolysis cell 10. In a water electrolysis stack 20 with the anode on top and the cathode on the bottom, gravity causes the supply water to be on the anode gas diffusion layer 13 side within the flow path 14a of the anode separator 14, and the generated oxygen to be on the opposite side. In addition, the produced water is separated from the cathode gas diffusion layer 16 within the flow path 17a of the cathode separator 17, and hydrogen is in contact with the cathode gas diffusion layer 16. However, in reality, due to the influence of the surface tension of water and the like, gas and liquid do not always separate in this manner, which hinders improvement in water electrolysis performance. 3, the inner surfaces (bottom surface 14b, side surface 14c) of the flow paths 14a of the anode separator 14 are water-repellent and therefore do not easily retain water, so the supply water is guided to the anode gas diffusion layer 13 side. Furthermore, the inner surfaces (bottom surface 17b, side surface 17c) of the flow paths 17a of the cathode separator 17 are hydrophilic and therefore easily attract water, so that the produced water is released from the cathode gas diffusion layer 16 and hydrogen easily flows out from the cathode gas diffusion layer 16. Therefore, water electrolysis is performed smoothly, and a decrease in water electrolysis performance can be suppressed. [Explanation of symbols]

[0030] 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 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; the cathode has a cathode catalyst layer, a cathode gas diffusion layer, and a cathode separator laminated on it from the solid polymer electrolyte membrane side; a flow path is formed in the anode separator, and only the wall surface of the flow path in the anode separator is made water-repellent; a flow path is formed in the cathode separator, the flow path being formed only on a wall surface of the cathode separator, and the surface of the wall surface facing the cathode gas diffusion layer is made hydrophilic; water electrolysis cell.

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

3. A water electrolysis stack comprising a plurality of water electrolysis cells according to claim 1 or 2 stacked together, The water electrolysis cells are stacked in a vertical direction and arranged with the anode at the top and the cathode at the bottom. Water electrolysis stack.

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