Water electrolysis cell

Abstract

This water electrolysis cell is provided with: an electrolyte layer; a first gas diffusion electrode layer disposed on one side of the electrolyte layer; a second gas diffusion electrode layer disposed on the other side of the electrolyte layer; a first catalyst layer disposed between the electrolyte layer and the first gas diffusion electrode layer; a second catalyst layer disposed between the electrolyte layer and the second gas diffusion electrode layer; and a water supply unit for supplying water to the surface of the first gas diffusion electrode layer on the side opposite the electrolyte layer.

Description

water electrolysis cell

[0001] The present disclosure relates to a water electrolysis cell that electrolyzes water to produce hydrogen and oxygen.

[0002] One example of a technology for generating hydrogen and oxygen is a water electrolysis cell, which electrolyzes water. A water electrolysis cell includes a proton (or anion) conductive porous electrolyte and a cathode and an anode composed of a material disposed on both sides of the porous electrolyte. The water electrolysis cell generates oxygen gas and hydrogen gas in the gas phase by supplying water to the porous electrolyte. Examples of such water electrolysis cells include those described in the following patent documents:

[0003] International Publication No. 2018 / 084175 International Publication No. 2020 / 085434

[0004] In conventional water electrolysis cells, for example, ladder-shaped members with slits formed in the gas diffusion electrode layer are formed, and water is supplied to the electrolyte layer through the slits. Therefore, processing is required to punch the slits in the gas diffusion electrode layer. This requires highly accurate alignment between the separator and the gas diffusion electrode layer (ladder-shaped members) during assembly of the water electrolysis cell, making the assembly of the water electrolysis cell difficult. Furthermore, since the slits are formed in the gas diffusion electrode layer, a water-repellent treatment must be performed on the gas diffusion electrode layer, which increases manufacturing costs. Furthermore, since the gas diffusion electrode layer is partially in contact with and pressed against the electrolyte layer, there is a concern that the reaction efficiency may decrease.

[0005] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a water electrolysis cell that reduces manufacturing costs and suppresses a decrease in reaction efficiency.

[0006] To achieve the above object, the water electrolysis cell of the present disclosure includes an electrolyte layer, a first gas diffusion electrode layer disposed on one side of the electrolyte layer, a second gas diffusion electrode layer disposed on the other side of the electrolyte layer, a first catalyst layer disposed between the electrolyte layer and the first gas diffusion electrode layer, a second catalyst layer disposed between the electrolyte layer and the second gas diffusion electrode layer, and a water supply unit that supplies water to a surface of the first gas diffusion electrode layer opposite to the electrolyte layer.

[0007] The water electrolysis cell of the present disclosure can reduce manufacturing costs and suppress a decrease in reaction efficiency.

[0008] Fig. 1 is a schematic diagram illustrating a water electrolysis cell according to a first embodiment. Fig. 2 is a plan view illustrating a gas diffusion electrode layer. Fig. 3 is a plan view illustrating a separator. Fig. 4 is a cross-sectional view illustrating the detailed configuration and operation of the water electrolysis cell according to the first embodiment. Fig. 5 is an exploded view illustrating a gas diffusion electrode layer in a water electrolysis cell according to a second embodiment.

[0009] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0010] First Embodiment <Schematic Configuration of Water Electrolysis Cell> FIG. 1 is a schematic diagram illustrating a water electrolysis cell according to a first embodiment.

[0011] As shown in FIG. 1 , the water electrolysis cell 10 includes an electrolyte layer 11, a first gas diffusion electrode layer 12, a second gas diffusion electrode layer 13, a first separator 14, and a second separator 15.

[0012] The electrolyte layer 11 is an electrolyte layer made of a solid electrolyte. In this embodiment, one side of the electrolyte layer 11 (the right side in FIG. 1 ) is the oxygen side, and the other side of the electrolyte layer 11 (the left side in FIG. 1 ) is the hydrogen side. However, the oxygen side and the hydrogen side may be reversed. For example, a proton-conductive dense body (solid polymer electrolyte) or a porous electrolyte is used as the solid electrolyte in the electrolyte layer 11, but the present invention is not limited thereto. Specific examples of the material include inorganic ceramics (such as hydrous titanium oxide nanoparticles). When an anion-conductive electrolyte is used, the electrolyte layer 11 may be, for example, a bipolar membrane or an anion exchange membrane.

[0013] The electrolyte layer 11 has a first gas diffusion electrode layer 12 and a first separator 14 arranged on one side, and a second gas diffusion electrode layer 13 and a second separator 15 arranged on the other side. Here, the first gas diffusion electrode layer 12 is an anode electrode on the oxygen side, and the second gas diffusion electrode layer 13 is a cathode electrode on the hydrogen side.

[0014] The first gas diffusion electrode layer 12 and the second gas diffusion electrode layer 13 are made of a porous material. The first gas diffusion electrode layer 12 and the second gas diffusion electrode layer 13 are preferably made of, but not limited to, Teflon (registered trademark)-modified porous carbon. The first gas diffusion electrode layer 12 and the second gas diffusion electrode layer 13 are provided with a first catalyst layer 32 and a second catalyst layer 37 (see FIG. 4 ) described below on the surfaces thereof that are bonded to the electrolyte layer 11. The first catalyst layer 32 and the second catalyst layer 37 are preferably made of, but not limited to, platinum-supported carbon. The first catalyst layer 32 and the second catalyst layer 37 may be provided on the surfaces of the first gas diffusion electrode layer 12 and the second gas diffusion electrode layer 13 that face the electrolyte layer 11, rather than on the surfaces of the first gas diffusion electrode layer 12 and the second gas diffusion electrode layer 13.

[0015] The first separator 14 is provided with a water supply unit 21. A water supply line L11 is connected to the water supply unit 21, and water is supplied from the outside through the water supply line L11. The first separator 14 is also provided with an oxygen gas discharge unit 22, and an oxygen discharge line L12 is connected to the oxygen gas discharge unit 22. On the other hand, the second separator 15 is provided with a hydrogen gas discharge unit 23, and a hydrogen discharge line L13 is connected to the hydrogen gas discharge unit 23.

[0016] When water is supplied from the water supply unit 21 to the first catalyst layer 32 of the first gas diffusion electrode layer 12, the supplied water is electrolyzed in the first catalyst layer 32 to produce oxygen (O ２ ) and hydrogen (H ２ ) is generated. At this time, the first gas diffusion electrode layer 12 functions as a cathode when electrolyzing water, and discharges the oxygen generated by electrolysis without containing water toward the oxygen gas discharge part 22. On the other hand, the second gas diffusion electrode layer 13 functions as an anode when electrolyzing water, and discharges the hydrogen generated by electrolysis without containing water toward the hydrogen gas discharge part 23.

[0017] In the region of the electrolyte layer 11 on the side of the first gas diffusion electrode layer 12, which functions as a cathode, oxygen is produced based on an electrolytic reaction according to the following formula: H ２ O → (1 / 2) O ２ +2H ＋ +2e － The reaction formula of the anion exchange membrane is as follows: － →O ２ +2H ２ O+4e － On the other hand, in the region of the second gas diffusion electrode layer 13, which functions as an anode, with respect to the electrolyte layer 11, hydrogen is produced based on an electrolytic reaction according to the following formula: 2H ＋ +2e － →H ２ The reaction formula of the anion exchange membrane is as follows: 2H ２ O + 2e － →2OH － +H ２

[0018] <Configuration of Gas Diffusion Electrode Layer> FIG. 2 is a plan view showing the gas diffusion electrode layer.

[0019] FIG. 2 is a plan view of the first gas diffusion electrode layer 12 as viewed from the electrolyte layer 11 side. The first gas diffusion electrode layer 12 includes a porous substrate 31 and a first catalyst layer 32. The porous substrate 31 has a rectangular plate shape. The first catalyst layer 32 is disposed on one side of the porous substrate 31. The first catalyst layer 32 has a comb shape. The first catalyst layer 32 includes a plurality of (four in this embodiment) first catalyst portions 32a disposed in parallel with a gap on the surface of the porous substrate 31, and one second catalyst portion 32b connecting each end of the plurality of first catalyst portions 32a. The porous substrate 31 has a predetermined region 33 on its surface, and the first catalyst layer 32 is disposed in the region 33. That is, the first catalyst layer 32 is applied to the region 33 of the porous substrate 31, and then pressed to form a smooth surface. Therefore, one surface and the other surface of the first gas diffusion electrode layer 12 are flat surfaces.

[0020] Although not shown, the second gas diffusion electrode layer 13 has substantially the same configuration as the first gas diffusion electrode layer 12, and includes a porous substrate 36 and a second catalyst layer 37 (see FIG. 4 for both).

[0021] <Configuration of Separator> FIG. 3 is a plan view showing the separator.

[0022] 3 is a plan view of the first separator 14 as seen from the first gas diffusion electrode layer 12 side. The first separator 14 has a substrate 41, a water supply channel 42, and a first gas discharge channel 43. The water supply channel 42 is part of the water supply unit 21 (see FIG. 1) and supplies water to the surface of the first gas diffusion electrode layer. The first gas discharge channel 43 is part of the oxygen gas discharge unit 22 (see FIG. 1) and discharges oxygen as the first gas generated by the oxygen gas discharge unit 22 to the outside.

[0023] The substrate 41 has a rectangular plate shape. The water supply channel 42 is disposed on one surface of the substrate 41. The water supply channel 42 is comb-shaped. The water supply channel 42 has a plurality (four in this embodiment) of first water channels 42a arranged in parallel with a gap on the surface of the substrate 41, and a plurality (three in this embodiment) of second water channels 42b connecting the ends of the plurality of first water channels 42a. The first gas discharge channel 43 is disposed on one surface of the substrate 41. The first gas discharge channel 43 is comb-shaped. The first gas discharge channel 43 has a plurality (four in this embodiment) of first gas channels 43a arranged in parallel with a gap on the surface of the substrate 41, and a plurality (three in this embodiment) of second gas channels 43b connecting the ends of the plurality of first gas channels 43a.

[0024] The water supply channels 42 and the first gas discharge channels 43 are alternately arranged on the surface of the substrate 41. That is, a plurality of first water channels 42a and a plurality of first gas channels 43a are alternately arranged parallel to each other with a gap between them. The second water channels 42b are arranged on one side of the in-plane direction of the substrate 41, and the second gas channels 43b are arranged on the other side of the in-plane direction of the substrate 41. The substrate 41 is provided with a sealant (sealing portion) 44 (see FIG. 4 ) that separates the water supply channels 42 and the first gas discharge channels 43.

[0025] Although not shown, the second separator 15 is substantially the same as the first separator 14, and includes a substrate 46, a second gas discharge channel 47, and a sealant (sealing portion) 48 (see FIG. 4). However, the second separator 15 does not include a water supply channel. The second gas discharge channel 47 is part of the hydrogen gas discharge portion 23 (see FIG. 1).

[0026] <Detailed Configuration of Water Electrolysis Cell> FIG. 4 is a cross-sectional view illustrating the detailed configuration and operation of the water electrolysis cell of the first embodiment.

[0027] 4 , the water electrolysis cell 10 is configured by stacking a first separator 14, a first gas diffusion electrode layer 12, an electrolyte layer 11, a second gas diffusion electrode layer 13, and a second separator 15. The first catalyst layer 32 is provided on the surface of the first gas diffusion electrode layer 12 and is thereby disposed between the electrolyte layer 11 and the first gas diffusion electrode layer 12. The second catalyst layer 37 is provided on the surface of the second gas diffusion electrode layer 13 and is thereby disposed between the electrolyte layer 11 and the second gas diffusion electrode layer 13. The water supply channel 42 and the first gas discharge channel 43 communicate with the surface of the first gas diffusion electrode layer 12 on which the first catalyst layer 32 is not provided. The second gas discharge channel 47 communicates with the surface of the second gas diffusion electrode layer 13 on which the second catalyst layer 37 is not provided.

[0028] During assembly of the water electrolysis cell 10, the sealant 44 is applied to the surface of either the first separator 14 or the first gas diffusion electrode layer 12, and the sealant 48 is applied to the surface of either the second separator 15 or the second gas diffusion electrode layer 13. As a result, the sealant 44 is disposed between the first separator 14 and the first gas diffusion electrode layer 12, and the sealant 48 is disposed between the second separator 15 and the second gas diffusion electrode layer 13. In this case, it is preferable to provide sealing grooves 12a, 13a on the surfaces of the first gas diffusion electrode layer 12 and the second gas diffusion electrode layer 13 so that the sealants 44, 48 enter the sealing grooves 12a, 13a.

[0029] When the water electrolysis cell 10 is assembled, the water supply channel 42 and the first gas discharge channel 43 in the first separator 14 face the first gas diffusion electrode layer 12, and are separated from each other by a sealant 44. The water supply channel 42 communicates with the surface of the first gas diffusion electrode layer 12 opposite to the electrolyte layer 11, thereby enabling water to be supplied to the first gas diffusion electrode layer 12. The first gas discharge channel 43 communicates with a position separated from the water supply channel 42 by the sealant 44 on the surface of the first gas diffusion electrode layer 12 opposite to the electrolyte layer 11, thereby enabling generated oxygen to be discharged.

[0030] The second separator 15 is provided with a second gas exhaust channel 47, which is defined by a sealant 48. The second gas exhaust channel 47 is connected to a position defined by the sealant 48 on the surface of the second gas diffusion electrode layer 13 opposite the electrolyte layer 11, thereby enabling the discharge of generated hydrogen.

[0031] <Operation of Water Electrolysis Cell> In the water electrolysis cell 10, water is supplied to the surface of the first gas diffusion electrode layer 12 from the water supply channel 42 of the first separator 14. A voltage is then applied to the first gas diffusion electrode layer 12 and the second gas diffusion electrode layer 13. The water that reaches the surface of the first gas diffusion electrode layer 12 from the water supply channel 42 passes through the inside of the first gas diffusion electrode layer 12 and reaches the end face of the first catalyst layer 32, where it is electrolyzed at the interface between the first catalyst layer 32 and the electrolyte layer 11, generating oxygen. The generated oxygen diffuses and permeates the inside of the first gas diffusion electrode layer 12, and is guided to the first gas discharge channel 43 of the first separator 14 and discharged.

[0032] Meanwhile, hydrogen ions generated by electrolysis of water at the interface between the first catalyst layer 32 and the electrolyte layer 11 permeate the electrolyte layer 11 and reach the interface between the electrolyte layer 11 and the second gas diffusion electrode layer 13, where hydrogen is generated. The generated hydrogen permeates while being diffused inside the second gas diffusion electrode layer 13, and is guided to the second gas discharge channel 47 of the second separator 15 and discharged.

[0033] At this time, the water supply channel 42 and the first gas exhaust channel 43 are separated by the sealant 44, so that water supplied to the surface of the first gas diffusion electrode layer 12 does not enter the first gas exhaust channel 43. Therefore, in the water electrolysis cell 10, water is supplied to the surface of the first gas diffusion electrode layer 12. The water supplied to the surface of the first gas diffusion electrode layer 12 passes through the inside of the first gas diffusion electrode layer 12, reaches the first catalyst layer 32, and is electrolyzed at the interface with the electrolyte layer 11.

[0034] Second Embodiment Fig. 5 is an exploded view showing a gas diffusion electrode layer in a water electrolysis cell according to a second embodiment. Note that components having the same functions as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0035] 5 , the first gas diffusion electrode layer 51 is configured by combining a first comb member 52 and a second comb member 53. The first comb member 52 is configured by disposing a first catalyst layer 62 on the surface of a comb-shaped porous substrate 61. The second comb member 53 is configured by disposing a first catalyst layer 62 on the surface of a comb-shaped porous substrate 66. Therefore, the first comb member 52 has a plurality of grooves 63 formed therein, and the second comb member 53 has a plurality of grooves 67 formed therein.

[0036] An adhesive 68 having a sealing function is applied to the plurality of grooves 63 or the plurality of grooves 67 of the first comb member 52 and the second comb member 53. The first comb member 52 and the second comb member 53 are combined so that the plurality of grooves 63 and the plurality of grooves 67 fit together, and are joined by the adhesive 68. The first gas diffusion electrode layer 51 composed of the first comb member 52 and the second comb member 53 has a rectangular plate shape, similar to the first gas diffusion electrode layer 12 of the first embodiment.

[0037] The second gas diffusion electrode layer may be fabricated in the same manner as the first gas diffusion electrode layer 51 .

[0038] [Effects of the present embodiment] The water electrolysis cell according to the first aspect comprises an electrolyte layer 11, a first gas diffusion electrode layer 12 disposed on one side of the electrolyte layer 11, a second gas diffusion electrode layer 13 disposed on the other side of the electrolyte layer, a first catalyst layer 32 disposed between the electrolyte layer 11 and the first gas diffusion electrode layer 12, a second catalyst layer 37 disposed between the electrolyte layer 11 and the second gas diffusion electrode layer 13, and a water supply unit 21 that supplies water to the surface of the first gas diffusion electrode layer 12 opposite to the electrolyte layer 11.

[0039] In the water electrolysis cell according to the first aspect, the first gas diffusion electrode layer 12 is made of a porous material and water is supplied to the surface of the first gas diffusion electrode layer 12. This eliminates the need to provide a slit in the first gas diffusion electrode layer 12 for supplying water, and eliminates the need for punching. Therefore, highly accurate alignment between the first separator 14 and the first gas diffusion electrode layer 12 is not required during assembly of the water electrolysis cell 10, facilitating assembly of the water electrolysis cell 10. Furthermore, water-repellent treatment of the first gas diffusion electrode layer 12 is not required, thereby reducing manufacturing costs. Furthermore, the electrolyte layer 11 and the first gas diffusion electrode layer 12 are in full contact with each other via the first catalyst layer 32, allowing uniform surface pressure to be applied, thereby preventing a decrease in reaction efficiency. Furthermore, minimizing the cross-sectional areas corresponding to the first separator 14 and the second separator 15 facilitates water penetration, thereby improving electrolysis performance.

[0040] In the water electrolysis cell according to the second aspect, a first separator 14 is disposed on the surface of the first gas diffusion electrode layer 12 opposite to the electrolyte layer 11. The first separator 14 is provided with a water supply channel 42 for supplying water to the surface of the first gas diffusion electrode layer 12 and a first gas discharge channel 43 for discharging generated oxygen (first gas). A sealant (sealing portion) 44 is provided between the first gas diffusion electrode layer 12 and the first separator 14 to separate the water supply channel 42 from the first gas discharge channel 43. As a result, the water supply channel 42 and the first gas discharge channel 43 are separated by the sealant 44 and function independently, thereby restricting the movement of water from the water supply channel 42 to the first gas discharge channel 43.

[0041] In the water electrolysis cell according to the third aspect, the first gas diffusion electrode layer 12 has a predetermined region 33 provided on its surface facing the electrolyte layer 11, and the first catalyst layer 32 is disposed in the region 33. This allows the surface of the first gas diffusion electrode layer 12 to be made flat and to be in close contact with the electrolyte layer 11 without any gaps.

[0042] In the water electrolysis cell according to the fourth aspect, the first gas diffusion electrode layer 12 and the second gas diffusion electrode layer 13 are configured by disposing a comb-shaped first catalyst layer 32 and a comb-shaped second catalyst layer 37 on the surface of a porous substrate, respectively. This improves the productivity of the first gas diffusion electrode layer 12 and the second gas diffusion electrode layer 13.

[0043] The water electrolysis cell according to the fifth aspect is the water electrolysis cell according to any one of the first to fourth aspects, and further includes a first gas diffusion electrode layer 51 (second gas diffusion electrode layer) formed by combining a first comb member 52 having a first catalyst layer 62 disposed on the surface of a comb-shaped porous substrate 61, and a second comb member 53 having a comb-shaped porous substrate 66 on the surface of which no catalyst layer is disposed. This allows the porous substrate 61 and the porous substrate 66 to be made of different materials as necessary.

[0044] REFERENCE SIGNS LIST 10 Water electrolysis cell 11 Electrolyte layer 12 First gas diffusion electrode layer 13 Second gas diffusion electrode layer 14 First separator 15 Second separator 21 Water supply section 22 Oxygen gas discharge section 23 Hydrogen gas discharge section 31 Porous substrate 32 First catalyst layer 32a First catalyst section 32b Second catalyst section 33 Region 36 Porous substrate 37 Second catalyst layer 41 Substrate 42 Water supply channel 42a First water channel 42b Second water channel 43 First gas discharge channel 43a First gas channel 43b Second gas channel 44 Sealant (sealing section) 46 Substrate 47 Second gas discharge channel 48 Sealant (sealing section) 51 First gas diffusion electrode layer 52 First comb member 53 Second comb member 61 Porous substrate 62 First catalyst layer 63 Groove section 66 Porous substrate 67 Groove portion 68 Adhesive L11 Water supply line L12 Oxygen discharge line L13 Hydrogen discharge line

Claims

1. A water electrolysis cell comprising: an electrolyte layer; a first gas diffusion electrode layer disposed on one side of the electrolyte layer; a second gas diffusion electrode layer disposed on the other side of the electrolyte layer; a first catalyst layer disposed between the electrolyte layer and the first gas diffusion electrode layer; a second catalyst layer disposed between the electrolyte layer and the second gas diffusion electrode layer; and a water supply unit that supplies water to a surface of the first gas diffusion electrode layer opposite to the electrolyte layer.

2. The water electrolysis cell according to claim 1, wherein a separator is disposed on the surface of the first gas diffusion electrode layer opposite to the electrolyte layer, the separator being provided with a water supply channel for supplying water to the surface of the first gas diffusion electrode layer and a first gas discharge channel for discharging the generated first gas, and a seal section is provided between the first gas diffusion electrode layer and the separator to separate the water supply channel from the first gas discharge channel.

3. The water electrolysis cell according to claim 1 or 2, wherein the first gas diffusion electrode layer has a predetermined area defined on its surface facing the electrolyte layer, and the first catalyst layer is disposed in the predetermined area.

4. The water electrolysis cell according to claim 1, wherein the first gas diffusion electrode layer and the second gas diffusion electrode layer are configured by disposing the first catalytic layer and the second catalytic layer, respectively, in a comb shape on the surface of a porous substrate.

5. The water electrolysis cell according to claim 4, wherein the first gas diffusion electrode layer and the second gas diffusion electrode layer are formed by combining a first comb member in which the first catalyst layer and the second catalyst layer are respectively arranged on the surface of a comb-shaped porous substrate, and a second comb member in which no catalyst layer is arranged on the surface of a comb-shaped porous substrate.

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