WO2018084175A1

WO2018084175A1 - Cell for water electrolysis/fuel cell power generation and cell stack body having a plurality of same cells stacked

Info

Publication number: WO2018084175A1
Application number: PCT/JP2017/039530
Authority: WO
Inventors: 理嗣曽根; 広重松本; 友規寺山; 崇雅土師; 笹森　理一; 佐藤　元彦
Original assignee: 国立研究開発法人宇宙航空研究開発機構; 国立大学法人九州大学; 京セラ株式会社
Priority date: 2016-11-01
Filing date: 2017-11-01
Publication date: 2018-05-11

Abstract

The present invention addresses the problem of providing a cell for water electrolysis/fuel cell power generation which is switchable between a water electrolysis mode and a fuel cell power generation mode, and, when switching from one mode to the other, is operational immediately in the mode after the switch. The present invention relates to the cell for water electrolysis/fuel cell power generation comprising, in a first direction substantially perpendicular to the cell stacking direction, a flow path for supplying or discharging water, in a second direction substantially perpendicular to the cell stacking direction, an oxygen-containing flow path for discharging or supplying an oxygen-containing gas, and, in a third direction substantially perpendicular to the cell stacking direction, a hydrogen-containing gas flow path for discharging or supplying a hydrogen-containing gas, wherein an oxygen-side electrode layer and a hydrogen-side electrode layer are water-repellent electrode layers.

Description

Water electrolysis / fuel cell power generation cell and cell laminate in which a plurality of cells are laminated

The present invention relates to a water electrolysis / fuel cell power generation cell capable of reversibly switching between water electrolysis and fuel cell power generation in a single cell, and a cell laminate in which a plurality of the cells are stacked.

In recent years, the use of hydrogen as an energy source has attracted attention for the use of renewable energy and the reduction of carbon dioxide emissions. Accordingly, research on fuel cells using hydrogen and oxygen as fuels and water electrolysis technology has been widely promoted. In solid polymer water electrolysis and fuel cell power generation, the basic structure of the cells used is similar, so that water electrolysis and fuel cell power generation can be switched reversibly in a single cell. Research on electrolysis / fuel cell power generation reversible cells has been conducted (see, for example, Patent Document 1).

In addition, one of the inventors of the present application has proposed a new water electrolysis cell for the purpose of generating hydrogen and oxygen at the gas phase interface (Patent Document 2). This water electrolysis cell is an electrode composed of a proton-conductive porous electrolyte and a water-repellent material (hereinafter also referred to as “water-repellent electrode”), and is bonded to both surfaces of the porous electrolyte. Electrodes (cathode and anode) and means for supplying water to the porous electrolyte, and oxygen gas and hydrogen gas can be generated in the gas phase.

In the water electrolysis cell proposed in Patent Document 2, hydrous titanium oxide nanoparticles are used as a porous electrolyte material. The water-repellent electrode is configured by supporting catalyst particles, platinum-supporting carbon is used as the catalyst, and Teflon (registered trademark) -modified porous carbon is used as the water-repellent conductive carrier. The water repellent electrode (anode and cathode) is composed of a gas diffusion electrode layer composed of a mixture of a semi-water repellent material and a catalyst on the joint surface side with the porous electrolyte, and an electrically conductive water repellent material on the outer side. It has a two-layer structure composed of a current collector layer.

According to the water electrolysis cell proposed in Patent Document 2, since hydrogen gas and oxygen gas are generated in the gas phase, the conventional structure of generating hydrogen gas and oxygen gas in the liquid phase is known. Compared with the water electrolysis cell, energy required for generating bubbles is unnecessary, and the efficiency is improved accordingly. Moreover, the water supplied to the porous electrolyte can be pressurized by using a water-repellent material that prevents only water from entering and passes only gas as the electrode material. This makes it possible to easily generate pressurized hydrogen or pressurized oxygen. If this characteristic is used, for example, when high-pressure hydrogen is supplied to a fuel cell vehicle, a hydrogen vehicle, etc., it is possible to greatly reduce the energy that needs to be increased.

JP 2011-146395 A Japanese Patent No. 5759687 JP 2004-134134 A

Conventional water electrolysis / fuel cell power generation reversible cells have a problem of water supply and water removal (drying) inside the cells when the operation mode is switched. That is, in the water electrolysis mode, water is supplied to the electrolyte layer, and hydrogen gas and oxygen gas generated in the electrolyte layer must be discharged to the outside of the cell. In the fuel cell power generation mode, the supplied hydrogen gas or oxygen is required. It is necessary to allow gas to pass through the gas diffusion layer and reach the electrode layer. In the fuel cell power generation mode, the gas diffusion layer portion needs to be dry, but the electrolyte portion needs to be wet because hydrogen gas must be in a proton (H ⁺ ) state. . As described above, in the water electrolysis mode and the fuel cell power generation mode, the performance (hydrophilicity / water repellency) required in each part inside the cell is contradictory, so the existing cell structure has satisfactory performance in both modes. It is not easy to get.

Also, Patent Document 1 proposes a reversible cell having means for supplying / drying water, but it takes a considerable time to switch the operation mode, and the operation is immediately switched from one mode to the other. Can't start. Moreover, although research regarding the optimization of the member which comprises a reversible cell is also performed (refer patent document 3), it has not reached practical use.

The present invention has been made under the above circumstances, and is easy to switch between the water electrolysis mode and the fuel cell power generation mode, and immediately after switching from one to the other, It is an object of the present invention to provide a water electrolysis / fuel cell power generation reversible cell that can be operated in a mode.

The present invention provides the following cells or cell laminates (1) to (8).
(1) Electrolysis of water supplied to the electrolyte by applying a voltage between the hydrogen side electrode and the oxygen side electrode, or the hydrogen side electrode and the electrolyte by the supplied hydrogen-containing gas and oxygen-containing gas And a water electrolysis / fuel cell power generation cell that performs fuel cell power generation at the oxygen side electrode,
An oxygen-side electrode layer, an electrolyte layer, a hydrogen-side electrode layer, a first gas separator that passes an oxygen-containing gas separated from liquid water between the oxygen-side electrode layer and the electrolyte layer, and the electrolyte layer A second gas separator that allows hydrogen-containing gas separated from liquid water to pass therethrough is laminated between the oxygen side electrode layer and the electrolyte layer, and / or A cell stack portion in which a catalyst layer is provided between the electrolyte layer and the hydrogen-side electrode layer;
A water flow path for supplying or discharging water in a first direction substantially perpendicular to the cell stacking direction;
An oxygen-containing gas flow path for discharging or supplying the oxygen-containing gas in a second direction substantially perpendicular to the stacking direction of the cells;
A hydrogen-containing gas flow path for discharging or supplying the hydrogen-containing gas in a third direction substantially perpendicular to the cell stacking direction;
With
A cell for water electrolysis / fuel cell power generation, wherein the oxygen side electrode layer and the hydrogen side electrode layer are water repellent electrode layers.
(2) A plurality of slits are formed in the oxygen side electrode layer,
A plurality of grooves communicating with the water flow path are formed on one surface of the first gas separator,
The first gas separator and the oxygen side electrode are stacked, the plurality of grooves are aligned with the plurality of slits of the oxygen side electrode, and water from the water channel is electrolyzed when water is electrolyzed. (1) A cell for water electrolysis / fuel cell power generation.
(3) A ladder-like member is formed between the plurality of slits of the oxygen-side electrode layer,
At least one oxygen-side vent hole penetrating to the other surface and communicating with the oxygen-containing gas flow path is formed in the ladder-like portion other than the plurality of grooves of the first gas separator,
The oxygen-side vent is aligned with the ladder-like member of the oxygen-side electrode layer, and the oxygen-containing gas that has passed through the oxygen-side electrode layer during the electrolysis of water is circulated through the oxygen-containing gas flow path (1 ) Or (2) water electrolysis / fuel cell power generation cell.
(4) In the second gas separator, at least one hydrogen side vent hole penetrating and communicating with the hydrogen-containing gas flow path is formed,
The water electrolysis / fuel cell power generation cell according to any one of (1) to (3), wherein the hydrogen-containing gas that has passed through the hydrogen-side electrode layer is circulated through the hydrogen-containing gas flow path during water electrolysis.
(5) Electrolysis of water supplied to the electrolyte by applying a voltage between the hydrogen side electrode and the oxygen side electrode, or the hydrogen side electrode and the electrolyte by the supplied hydrogen-containing gas and oxygen-containing gas And a water electrolysis / fuel cell power generation cell that performs fuel cell power generation at the oxygen side electrode,
A first gas diffusion / separator, an oxygen side electrode layer held by the first gas diffusion / separator, an electrolyte layer and an electrolyte holding unit for holding the same, a hydrogen side electrode layer, a first for holding the hydrogen side electrode layer A cell stack portion in which two gas diffusion / separators are stacked and a catalyst layer is provided between the oxygen side electrode layer and the electrolyte layer and / or between the electrolyte layer and the hydrogen side electrode layer; ,
An oxygen-containing gas flow path provided in a second direction substantially perpendicular to the stacking direction of the first gas diffusion and separator;
A hydrogen-containing gas flow path provided in the third direction substantially perpendicular to the stacking direction and the second direction in the second gas diffusion and separator;
A water flow path provided in the electrolyte holding unit in a first direction substantially perpendicular to the stacking direction, supplying water from a side surface of the layer containing the electrolyte, or discharging water;
A cell for water electrolysis / fuel cell power generation, wherein the oxygen side electrode layer and the hydrogen side electrode layer are water repellent electrode layers.
(6) The water electrolysis / fuel cell power generation cell according to any one of (1) to (5), wherein the electrolyte is a proton (H ⁺ ) conductive porous electrolyte and / or a dense electrolyte.
(7) The water electrolysis / fuel cell power generation according to any one of (1) to (6), wherein one or both of the oxygen side electrode layer and the hydrogen side electrode layer comprises Teflon (registered trademark) modified porous carbon. Cell.
(8) A cell stack comprising two or more cells according to any one of (1) to (7) stacked in the stacking direction, wherein at least some of the water flow paths in each cell are mutually connected. Connected, at least part of the oxygen flow path in each cell is connected to each other, at least part of the hydrogen flow path in each cell is connected to each other, and at least part of the oxygen-side electrode layer in each cell Are electrically connected to each other, and at least some of the hydrogen-side electrode layers in each of the cells are electrically connected to each other.

According to the present invention, the water electrolysis / fuel cell can be switched between the water electrolysis mode and the fuel cell power generation mode, and can be immediately operated in the mode after switching when switching from one to the other. A power generation reversible cell can be provided.

FIG. 3 is a perspective view showing a cell stack according to the first embodiment. FIG. 2 is an exploded view showing components constituting the cell stack shown in FIG. 1 separated from each other in the direction of an arrow. It is a top view of a gas separator. It is the perspective view which showed only the groove | channel and plate-shaped part of a gas separator. FIG. 4 is a cross-sectional view taken along a line AA in FIG. 3 perpendicular to the paper surface. It is the top view which showed the positional relationship of the gas separator and gas diffusion electrode layer when a cell was assembled. It is the enlarged view which showed typically the cross section which cut one cell of the cell stack of the state completed by combining each component shown in FIG. 2 perpendicularly to the plate-shaped part. It is a perspective view which shows the cell stack which concerns on this Embodiment 2. FIG. FIG. 9 is an exploded view showing components constituting the cell stack shown in FIG. 8 separated from each other in the direction of the arrow. It is a top view of a solid electrolyte holding part. It is a top view of the gas diffusion and separator on the oxygen side. FIG. 10 is an enlarged view schematically showing a cross section of one cell of the cell stack in a state completed by combining the components shown in FIG. 9, taken along line BB in FIG. 10. It is sectional drawing which shows the state which transcribe | transferred the water repellent to the edge part of carbon paper. It is sectional drawing which shows the state which coat | covered the water-repellent agent with the ladder-like carbon paper as GDL. It is a figure which shows the SEM image of the surface which water-repellent-treated the gas diffusion electrode layer.

Hereinafter, the present embodiment will be described, but the present invention is not limited to the following embodiment.
Further, in the following description, there is a description of “oxygen”, “oxygen gas”, “hydrogen”, “hydrogen gas”, but it may be “oxygen-containing gas” or “hydrogen-containing gas”. Also good.

[Embodiment 1]
FIG. 1 is a perspective view showing a cell stack 5 according to the first embodiment, and FIG. 2 shows the components constituting the cell stack 5 shown in FIG. It is an exploded view. The cell stack 5 shown in FIG. 1 is assembled by bringing the components shown in FIG. 2 into close contact with each other and fastening the eight bolts 50 ₁ to 50 ₈ and the corresponding nuts.

The cell stack 5 in FIG. 1 is a stack of two water electrolysis / fuel cell power generation reversible cells (hereinafter sometimes simply referred to as “cells”) in the direction indicated by the arrow 6. to be configured from the multilayer part 21 _1-27 ₁ and the end plate 31 shown, the second cell is composed of end plates 33 and laminate part 21 _2-27 ₂ shown in FIG. The intermediate plate 32 is shared by both the first and second cells. In the first cell and the second cell shown in FIG. 2, parts with the same reference numerals that differ only in the subscript are parts corresponding to each other and share the same function. Therefore, only the first cell will be described below, and the subscript will also be described. Omitted unless necessary.

In FIG. 2, the component indicated by reference numeral 24 is an electrolyte layer made of a solid electrolyte. In the present embodiment, the left side of the electrolyte layer 24 is arranged on the oxygen side, and the right side of the electrolyte layer 24 is arranged on the hydrogen side. However, the arrangement of the oxygen side and the hydrogen side may be reversed.

The gasket 23, the gas separator 22, the gasket 21, and the intermediate plate 32 are disposed on the left side (oxygen side) of the electrolyte layer 24. On the other hand, a gasket 25, a gas separator 26, a gasket 27, and an end plate 31 are arranged on the right side (hydrogen side) of the electrolyte layer 24. A square gas diffusion electrode layer 35 is fitted in the central portion of the oxygen-side gasket 23. The gas diffusion electrode layer 35 becomes an oxygen side electrode layer. The gas diffusion electrode layer 35 is provided with a plurality of parallel slits 45 (described later). On the other hand, a rectangular gas diffusion electrode layer 36 without a slit is fitted in the center of the hydrogen-side gasket 25. The gas diffusion electrode layer 36 becomes a hydrogen side electrode.

FIG. 3 is a plan view with the right side of the gas separator 22 (the side not visible in FIG. 2) facing up. As shown in FIG. 3, six parallel grooves 60 ₁ to 60 ₆ dug in the thickness direction (direction perpendicular to the paper surface of FIG. 3) are formed in the central portion of the gas separator 22. As a result, elongated plate-like portions 61 ₁ to 61 ₅ are formed between the grooves. FIG. 4 is a perspective view showing only the groove 60 and the plate-like portion 61 shown in FIG. As shown in FIG. 4, the plate-like portions 61 ₁ to 61 ₅ and parallel opposite edges and which, vent holes 62 _1-62 ₇ is provided. Each of the vent holes 62 ₁ to 62 ₇ passes through the gas separator 22.

FIG. 5 is a cross-sectional view taken along a line AA in FIG. 3 in a direction perpendicular to the paper surface. As shown in the figure, a water flow path 63 is formed in a tunnel shape inside the gas separator 22. One of the water channels 63 is connected to the

water channels

51 and 52 shown in FIG. 1, and the other is connected to the grooves 60 ₁ to 60 ₆ . Although the

water flow paths

51 and 52 shown in FIG. 1 extend in parallel with the arrow 6, the water flow path 63 formed inside the gas separator 22 has a direction perpendicular to the arrow 6, that is, a direction perpendicular to the cell stacking direction. It extends to. Thus, by providing the water flow path 63 in a direction perpendicular to the cell stacking direction, a plurality of cells can be stacked in a compact manner.

FIG. 6 is a plan view showing the positional relationship between the gas separator 22 and the gas diffusion electrode layer 35 when the cell is assembled. Actually, as shown in FIG. 2, the gas diffusion electrode layer 35 is fitted into the gasket 23. By assembling the entire cell including the gasket 23, the gas separator 22 and the gas diffusion electrode layer 35 are shown in FIG. Positional relationship.

As shown in FIG. 6, the slits 45 ₁ to 45 ₆ provided in the gas diffusion electrode layer 35 are aligned with the corresponding grooves 60 ₁ to 60 ₆ provided in the gas separator 22. Ladder member 46 _1-46 ₇ between the slit and the slit of the gas diffusion electrode layer 35 is aligned with the corresponding plate-shaped portions 61 ₁ to 61 ₅ and parallel opposite edges and these gas separator 22, the plate The portions 61 ₁ to 61 ₅ and the vent holes 62 ₁ to 62 ₇ provided at the edges on both sides are closed. Thus, it is possible to prevent water from entering the vent holes 62 _1-62 ₇ as will be described later.

As shown in FIG. 2, a plurality of grooves are also formed on the left surface of the gas separator 26, but this is not essential as in the case of the gas separator 22.

2) Carbon paper (not shown) is fitted in the center of the gaskets 21 and 27 shown in FIG. The carbon paper fitted into the gasket 27 diffuses hydrogen gas passing therethrough and communicates with the hydrogen gas flow path 65 provided on the left surface of the end plate 31. The hydrogen gas flow path 65 is connected to a flow path 66 provided on the lower side, and communicates with the hydrogen gas flow path 54 shown in FIG. On the other hand, the gas diffusion layer fitted in the gasket 21 diffuses oxygen gas passing therethrough, and communicates with oxygen gas passages provided on the right side of the intermediate plate 32 (side not visible in FIG. 2). These oxygen gas flow paths are connected to a flow path 68 provided on the upper side thereof, and communicate with the oxygen gas flow path 53 shown in FIG.

FIG. 7 is an enlarged view schematically showing a cross section of one cell of the cell stack 5 in a state completed by combining the components shown in FIG. FIG. In FIG. 7, the above-mentioned carbon paper is omitted because it is not an essential component. As shown in FIG. 7, the electrolyte layer 24 is in the center, with the oxygen side above it and the hydrogen side below it.

As the solid electrolyte constituting the electrolyte layer 24, a proton (H ⁺ ) conductive porous electrolyte can be used. As a specific material, inorganic ceramics (for example, hydrous titanium oxide nanoparticles) disclosed in Patent Document 2 can be suitably used. As another example of the solid electrolyte constituting the electrolyte layer 24, a proton conductive Nafion (registered trademark) which is a dense electrolyte can be used.

As materials for the oxygen-side gas diffusion electrode layer 35 and the hydrogen-side gas diffusion electrode layer 36 sandwiching the electrolyte layer 24, for example, Teflon (registered trademark) modified porous carbon disclosed in Patent Document 2 is preferably used. be able to. By using this material, oxygen gas and hydrogen gas can pass through the inside. Further, the gas diffusion electrode layer 35 and the gas diffusion electrode layer 36 are subjected to water repellency treatment as a whole and have strong water repellency. As a result, water can be prevented from entering the gas diffusion electrode layer 35 and the gas diffusion electrode layer 36.

Catalyst layers 35 ₁ and 36 ₁ are formed on the surfaces of the gas diffusion electrode layer 35 and the gas diffusion electrode layer 36 on the side to be joined to the electrolyte layer 24, respectively. As the catalyst material, platinum-supported carbon disclosed in Patent Document 2 can be suitably used. It is sufficient that the catalyst has several atomic layers. For this purpose, for example, a method of spraying the catalyst material by spraying can be applied. Here, the catalyst layers are formed on the oxygen-side gas diffusion electrode layer 35 and the hydrogen-side gas diffusion electrode layer 36, but a catalyst layer may be formed on the surface of the electrolyte layer 24.

In the water electrolysis mode, a voltage is applied to the gas diffusion electrode layers 35 and 36. As a result, oxygen gas generated at the interface (catalyst layer) between the gas diffusion electrode layer 35 and the electrolyte layer 24 passes through the ladder member 46 of the gas diffusion electrode layer 35 and passes through the air holes 62 ₁ to 62 of the gas separator 22. ₁ and is diffused by carbon paper (not shown) through this, and then passes through a gas flow path 67 and a flow path 68 provided in the intermediate plate 32 or the end plate 33, and then the oxygen gas shown in FIG. It is discharged from the flow path 53 to the outside. On the other hand, the hydrogen gas generated at the interface (catalyst layer) between the gas diffusion electrode layer 36 and the electrolyte layer 24 passes through the inside of the planar gas diffusion electrode layer 36 while being diffused, and enters the vent hole 64 of the gas separator 26. After being guided and diffused by gas carbon paper (not shown), the gas flow path 65 _{and the} flow path 66 provided in the end plate 31 are passed through the hydrogen gas flow path 54 shown in FIG. Is discharged.

As described above, the gas diffusion electrode layers 35 and 36 have strong water repellency. Thereby, water supplied from the outside to the electrolyte layer 24 through the water flow path 63, the grooves 60 ₁ to 60 ₆ and the slits 45 ₁ to 45 ₆ does not enter the gas diffusion electrode layers 35 and 36. Therefore, the path of oxygen gas and hydrogen gas and the path of water are completely separated, and they do not mix. Thus, in the cell of this embodiment, water is directly supplied to the electrolyte layer 24 made of a solid electrolyte in the water electrolysis mode. The supplied water is blocked by the water-repellent gas diffusion electrode layers 35 and 36 and does not enter the gas diffusion electrode layers 35 and 36 or the

gas separators

22 and 26. That is, the water path, the oxygen gas path, and the hydrogen gas path are completely independent and separated from each other.

On the other hand, in the fuel cell power generation mode, the flow until oxygen gas and hydrogen gas supplied from the outside reaches the electrolyte layer 24 and the flow of water generated in the electrolyte layer 24 are opposite to those in the water electrolysis mode. At this time, since the gas diffusion electrode layer 35 and the gas diffusion electrode layer 36 have strong water repellency, the supplied oxygen gas and hydrogen gas can be pressurized. By pressurizing oxygen gas and hydrogen gas, water generated in the electrolyte layer 24 is urged toward the slits 45 ₁ to 45 ₆ and is smoothly discharged.

With the configuration as described above, the cell stack 5 of the present embodiment does not cause water clogging even when the water electrolysis mode is switched to the fuel cell power generation mode, and stably in the fuel cell power generation mode immediately after the switching. Driving is possible. Further, even when the fuel cell power generation mode is switched to the water electrolysis mode, the operation in the water electrolysis mode can be performed immediately after the switching. In particular, in the switching between the fuel cell power generation mode and the water electrolysis mode, the process of drying / supplying the water required in the conventional cell is not required, so that it can be used as a reversible cell that can be switched seamlessly. .

Further, as described above, the supply and discharge of water are performed in the first direction substantially perpendicular to the stacking direction, and the supply and discharge of oxygen gas and hydrogen gas are performed in the second and substantially perpendicular directions to the stacking direction, respectively. By performing in the third direction, by stacking a plurality of cells, the first cell and the second cell, a compact dimension in the stacking direction can be realized, and the water electrolysis cell and the fuel cell power generation cell Ability can be improved.

[Embodiment 2]
FIG. 8 is a perspective view showing the cell stack 70 according to the second embodiment of the present invention, and FIG. 9 is a diagram showing the components constituting the cell stack 70 shown in FIG. It is the exploded view shown. The cell stack 70 shown in FIG. 8 is assembled by bringing the components shown in FIG. 9 into close contact with each other and fastening bolts and nuts (not shown). The cell stack 70 of the second embodiment shown in FIG. 8 is composed of one water electrolysis / fuel cell power generation reversible cell. However, any number of cells can be stacked in the direction indicated by the arrow 6 as in the cell stack 5 of the first embodiment. For this reason, the term “cell stack (cell stack)” is also used in this embodiment for convenience.

Among the components shown in FIG. 9, a component denoted by reference numeral 86 disposed in the center between the two

end plates

80 and 92 is a solid electrolyte holding portion, and the left side of the drawing as viewed from the solid electrolyte holding portion 86 is oxygen. The right side and the right side are arranged on the hydrogen side. However, as in the first embodiment, the arrangement of the oxygen side and the hydrogen side may be reversed. In the actual cell stack 70, various gaskets may be used depending on the situation, but the illustration is omitted here for the sake of simplicity. The member 82 is an oxygen side gas diffusion and separator, and the member 90 is a hydrogen side gas diffusion and separator.

FIG. 10 is a plan view of the solid electrolyte holding portion 86. The central portion of the solid electrolyte retention portion 86, central opening 86 ₁ is formed. The central opening 86 ₁ is described solid electrolyte 95 (Fig. 12) is fitted. As the solid electrolyte, as in the first embodiment, a proton (H ⁺ ) conductive porous electrolyte or a proton conductive Nafion (registered trademark) which is a dense electrolyte can be used. Further, it may be a solid electrolyte containing both a porous electrolyte and a dense electrolyte.

As shown in FIG. 10, on the central opening 86 ₁ of the solid electrolyte retention portion 86 opening 86 ₂ is provided. The number of water passage 86 ₄ is formed between the central opening 86 ₁ and the opening portion 86 _2, and connects between the central opening 86 ₁ and the opening portion 86 _2. Similarly, under the central opening 86 _first opening 86 ₃ is provided, a large number of water passage 86 ₅ is formed between the central opening 86 ₁ and the opening portion 86 _3, central opening 86 ₁ and the opening portion 86 ₃ Are connected. In addition, the water channel which connects a center opening and an opening part may be one if water can be distribute | circulated.

The

openings

86 ₂ and 86 ₃ are connected to the water flow paths 75 ₁ and 75 ₂ shown in FIG. 8 when the cell stack 70 is assembled. Thus, the water electrolysis mode, the water supplied from the water passage 75 ₁ and 75 _2, supplied to the solid electrolyte 95 which is fitted in a central opening 86 through the opening 86 _2, 86 ₃ through the water passage 86 _4, 86 ₅ Is done. Forming direction of the

water flow path

86 ₄ and 86 _5, the stacking direction of the cell stack (the direction indicated by arrow 6) and perpendicular. Thus, that it is possible to stack a plurality of cells by providing the water channel 86 _4, 86 ₅ in the stacking direction perpendicular to the direction is the same as the first embodiment. However, in Embodiment 1, water is finally supplied to the catalyst layer on the surface side of the solid electrolyte, whereas in Embodiment 2, water is supplied to the side surface side of the solid electrolyte as can be seen from FIG. .

FIG. 11 is a plan view of the gas diffusion / separator 82 on the oxygen side. The gas diffusion and separator 90 on the hydrogen side has the same structure. A recess 82 ₁ is formed at the center of the gas diffusion / separator 82. The recess 82 ₁ is adapted to the shape of the gas diffusion electrode layer. As a material for the gas diffusion electrode layer, as in the first embodiment, Teflon (registered trademark) -modified porous carbon shown in Patent Document 2 can be suitably used. The use of this material allows oxygen gas and hydrogen gas to permeate through the interior of the material, and as a whole, water repellent treatment is applied to provide strong water repellency, so that water is a gas diffusion electrode layer. The point which cannot penetrate | invade into the inside of is also the same as that of Embodiment 1.

As shown in FIG. 11, an opening 82 ₂ is provided on the left side of the recess 82 ₁ . Further, between the recesses 82 ₁ and the opening portion 82 _2, a number of grooves 82 ₃ is formed, which connects the recess 82 ₁ and the opening portion 82 _2. In addition, the groove | channel which connects a recessed part and an opening part may be one if a gas can be distribute | circulated. When the cell stack 70 is assembled, the oxygen-side gas diffusion / separator 82 and the hydrogen-side gas diffusion / separator 90 shown in FIG. 11 are arranged so as to face each other with a solid electrolyte therebetween. Therefore, in the oxygen side gas diffusion and separator 82 shown in FIG. 9, a groove 82 ₃ is provided on the right side of FIG. 9, and in the hydrogen side gas diffusion and separator 90, a groove 90 ₃ (not shown) is provided on the left side of FIG. Is provided). Therefore, when the cell stack 70 is assembled, the groove 82 ₃ shown in FIG. 11 communicates with the gas flow path 77 and the groove 90 ₃ communicates with the gas flow path 76. In the water electrolysis mode, the oxygen gas generated on the oxygen side reaches the opening 82 ₂ through the groove 82 ₃ and is guided to the gas flow path 77 from there. On the other hand, the hydrogen gas generated on the hydrogen side reaches the opening 90 ₃ through the groove 90 ₃ and is guided to the gas flow path 76 from there.

FIG. 12 is an enlarged view schematically showing a cross section of a central region taken along the line BB of FIG. 10, showing one cell of the cell stack 70 in a state completed by combining the components shown in FIG. is there. As shown in FIG. 12, there is a solid electrolyte 95 in the center, an oxygen-side gas diffusion electrode layer 96 on the upper side, and a hydrogen-side gas diffusion electrode layer 97 on the lower side. Further, the solid electrolyte 95, because they are fitted in the central opening 86 ₁ of the solid electrolyte retention portion 86, as described above, the periphery of the solid electrolyte 95, in particular side surfaces of the left and right of FIG. 12 is stopped closing so as not to enter and exit the water . Catalyst layers 98 and 99 are formed on the surfaces of the gas diffusion electrode layer 96 and the gas diffusion electrode layer 97 on the side in contact with the solid electrolyte 95. The material and formation method of the catalyst layer are the same as those in the first embodiment. Here, the catalyst layers are formed on the gas diffusion electrode layer 96 and the hydrogen-side gas diffusion electrode layer 97, but a catalyst layer may be formed on the surface of the solid electrolyte 95.

In the water electrolysis mode, a voltage is applied to the gas diffusion electrode layers 96 and 97. The water, as described above, and supplies the water passage 75 ₁ and 75 _2, the openings 86 _2, 86 _3, water channel 86 _4, 86 ₅ solid electrolyte 95 fitted to the central opening 86 through. Therefore, in FIG. 12, water is supplied to the solid electrolyte 95 from a direction perpendicular to the paper surface. As a result, the oxygen gas generated at the bonding interface between the gas diffusion electrode layer 96 and the solid electrolyte 95 is guided to the right in the gas diffusion electrode layer 96 as shown by arrows in FIG. It reaches the opening 82 ₂ through 82 _3, and is discharged from here through the gas flow path 77. On the other hand, the hydrogen gas generated at the bonding interface between the gas diffusion electrode layer 97 and the solid electrolyte 95, as shown by the arrows in FIG. 12, is led through the gas diffusion electrode layer 97 to the left side, through the groove 90 ₃ It reached the opening 90 ₂ is discharged to the outside through the gas passage 76 from here.

In the fuel cell power generation mode, the flow until oxygen gas and hydrogen gas supplied from the outside reaches the solid electrolyte 95 and the flow of water generated in the solid electrolyte 95 are opposite to those in the water electrolysis mode. Also in Embodiment 2, since the gas diffusion electrode layers 96 and 97 have strong water repellency, the supplied oxygen gas and hydrogen gas can be pressurized. By pressurizing the oxygen gas and hydrogen gas, the water generated in the solid electrolyte 95, it is urged toward the water channel 86 _4, 86 _5, and is discharged smoothly.

As described above, the gas diffusion electrode layers 96 and 97 are subjected to water repellent treatment and have strong water repellency. Thus, the water supplied to the solid electrolyte 95 through the water passage 86 _4, 86 ₅ from the outside, it does not enter into the gas diffusion electrode layers 96 and 97. Therefore, the path of oxygen gas and hydrogen gas and the path of water are completely separated, and they do not mix. Therefore, even when the water electrolysis mode is switched to the fuel cell power generation mode, water clogging does not occur, and the operation in the fuel cell power generation mode can be stably performed immediately after the switching, as in the case of the first embodiment. is there.

In addition, as described above, the supply and discharge of water are performed in the first direction substantially perpendicular to the stacking direction, and the supply and discharge of oxygen gas and hydrogen gas are performed in the second and substantially perpendicular directions to the stacking direction, respectively. By performing in the third direction, it becomes possible to stack a plurality of cells, to realize a compact size in the stacking direction, and to improve the capacity of the water electrolysis cell and the fuel cell power generation cell. Is the same as that of the first embodiment.

[Embodiment 3]
Next, water repellency treatment of the gas diffusion electrode layer will be described as Embodiment 3. The gas diffusion electrode layer referred to in this embodiment is a material having a property of permeating hydrogen and oxygen generated during water electrolysis and used as an anode electrode or a cathode electrode. Generally, a gas diffusion layer (GDL) is also used. be called. As a base material for the gas diffusion electrode layer, for example, carbon paper with MPL (microporous layer) can be used. The thickness of the carbon paper used is about 0.16 mm. However, MPL is not always necessary. Such a carbon paper has a certain degree of mechanical strength, is electrically conductive, and has a characteristic of good gas permeability (good gas permeability). However, since this material does not have sufficient water repellency as it is, it is necessary to perform treatment (water repellency treatment) for imparting sufficient water repellency to the gas diffusion electrode layer.

The method of water repellent treatment of carbon paper in this embodiment is performed according to the following procedure. First, prepare a water repellent. As the water repellent, a fluid obtained by dissolving acetylene black (AB) and polytetrafluoroethylene (PTFE) in a solvent at a predetermined ratio can be used. This fluid water-repellent agent is applied on each of the two aluminum foils serving as a transfer base so as to have an area sufficient to cover all of the carbon paper to be used, and dried as necessary.

Next, the carbon paper is sandwiched from both sides in a sandwich shape so that the surface to which the water repellent is applied is in contact with the surface of the carbon paper. This is mounted on a hot press machine and heated while being pressurized at a temperature of, for example, 360 ° C. exceeding the melting point (327 ° C.) of PTFE for several minutes. By doing so, the water repellent is reversely transferred from the two aluminum foils to the carbon vapor. And after cooling this, an aluminum foil is removed. As a method for removing the aluminum foil, it may be directly removed mechanically, but it is preferable to chemically remove the aluminum foil on the surface by dipping in an acidic solution (for example, a NaCL solution). As a result, the entire carbon paper is uniformly coated with the water repellent.

FIG. 13A is a cross-sectional view showing the state of the end of the carbon paper 100 after the carbon paper 100 is coated with the water repellent 102 by the above-described method. In FIG. 13A, the side surface of the carbon paper 100 is completely in contact with the water repellent. This is presumably because the water repellent that became a fluid wraps around the sides of each ladder-like branch by heating and pressurizing with a hot press. However, it is sufficient that the carbon paper is sealed with a water repellent, and there may be a slight gap between the side surface of the carbon paper and the water repellent 102 as shown in FIG. If it is sufficient to coat the water repellent only on one side of the carbon paper 100, as shown in FIG. 13 (c), the water repellent is applied to only one aluminum foil, so that the carbon repellent is applied. It is also possible to reversely coat the water repellent 102 on only one side of the paper 100. In FIGS. 13A to 13C, the thicknesses of the carbon paper 100 and the coated water repellent 102 are exaggerated from the actual ones. By covering the carbon paper 100 with the water repellent 102 by the reverse transfer method of the water repellent as described above, it is possible to give the carbon paper a predetermined water repellency while maintaining the electrical conductivity of the carbon paper. it can.

FIG. 14 is a cross-sectional view illustrating a state in which the carbon paper 100 having the same shape as that of the ladder-like gas diffusion electrode layer 35 illustrated in FIG. However, FIG. 14 shows the thickness of the carbon paper 100 and the coated water repellent 102 exaggerated from the actual one. As shown in the figure, the carbon paper 100 is covered with a water repellent 102 not only on the upper and lower surfaces but also on the side surfaces of each ladder-like branch. Thereafter, a catalyst layer is formed on the surface in contact with the electrolyte to form the gas diffusion electrode layer 35. However, the catalyst layer can also be formed on the carbon paper 100 before the water repellent layer 102 is formed.

According to the water-repellent gas diffusion electrode layer of this embodiment, it becomes possible to apply more pressure than ever before to water supplied during water electrolysis, and it is possible to improve performance as a water electrolysis cell. As shown in FIG. 7, the water repellency is improved by covering the side surface of each ladder-like branch of the gas diffusion electrode layer 35 with the water-repellent agent 102, and water from the side surface of each branch is improved. The intrusion can be completely blocked.

The characteristics of the third embodiment are summarized as follows.
(1) applying a fluid water repellent to the transfer substrate;
A step of covering one surface or both surfaces of a planar gas diffusion layer at a portion where the water repellent of the transfer substrate is applied;
Heating the gas diffusion layer covered with the transfer substrate while applying pressure to transfer the water repellent to the gas diffusion layer;
Removing the transfer substrate after transfer;
A water repellent treatment method for a gas diffusion layer.
(2) As the water repellent of the fluid, a solution obtained by dissolving acetylene black and polytetrafluoroethylene in a solvent at a predetermined ratio can be used.
(3) The temperature at the time of heating in the transferring step can be higher than the melting point of polytetrafluoroethylene.
(4) Carbon paper can be used as the gas diffusion layer.
(5) A hot press machine can be used for the transferring step.

Examples of the third embodiment will be described below. In addition, this invention is not limited to a following example.
The water repellency treatment of the gas diffusion electrode layer was performed as follows.
[1] Preparation of spray coating solution as water repellent (1) To a 300 mL beaker, 1.0 g of Triton-X, 95 mL of distilled water and 5 mL of ethanol were added and stirred.
(2) 2.0 g of Acetylene Black (AB) was added and stirred for 5 minutes.
(3) Ultrasonic dispersion was performed for 15 minutes.
(4) A ball mill (YTZ ball φ2.0 mms) was performed for 1 day.
(5) 20 g of PTFE dispersion (60 wt%) was added.
(6) A ball mill (YTZ ball φ2.0 mm) was performed for 1 hour.
(7) Filtration was performed with a membrane filter (pore size: 5.0 μm).
A spray coating solution having an AB / PTFE weight ratio (PTFE volume ratio) of 1/6 (84%) was obtained.
[2] Film formation by reverse transfer (1) Coating was carried out on an aluminum foil using a spray coater at a hot plate temperature of 200 ° C.
(2) It was performed by vacuum drying (temperature 200 ° C.) for 15 minutes.
(3) MPL carbon paper (GDL29BC) cut to φ22 mm was prepared, and both sides were sandwiched between coated aluminum foils.
(4) Hot pressing (260 kg / cm ² , 3 minutes) was performed at a predetermined temperature (280 ° C., 320 ° C., 360 ° C.).
(5) After hot pressing, the aluminum foil was dissolved by dipping in a 5M NaCl aqueous solution.
(6) Washed with distilled water.
(7) The scissors were cut with a cutter.
[3] Observation Result by SEM FIG. 15 shows an SEM image of the sample after reverse transfer. (A) is an SEM image without reverse transfer, (b) is an SEM image when hot pressed at 280 ° C., (c) is an SEM image when hot pressed at 320 ° C., and (d) is 360 ° C. It is a SEM image at the time of hot-pressing by. Cracks were observed in the samples having hot press temperatures of 280 ° C. and 320 ° C. Even when the water pressure resistance test was actually carried out, water leakage occurred at 0.01 MPa. On the other hand, in the case where the hot pressing temperature was 360 ° C. (FIG. 15D), no crack was observed. The water pressure test was cleared to 0.3 MPa. This was thought to be because the PTFE particles were transferred in a dissolved state by performing hot pressing at a melting point (327 ° C.) or higher of PTFE. Further, the gas permeability was 4 mL / atm cm ² min, and the gas permeability was confirmed.

5 Cell stack (cell stack)
21, 23, 25, 27

Gasket

22, 26 Gas separator 24

Electrolyte layer

31, 33 End plate 32

Intermediate plate

35, 36 Gas diffusion electrode layer 45

Slit

51, 52 Water flow channel 54 Hydrogen gas flow channel 60 Groove 62 Vent hole 63

Water flow road

65,67 gas channel 66, 68 the channel 70

cell stack

76, 77

gas passages

80,92

end plates

82 and 90 the gas diffusion and the separator 86 solid electrolyte retention portion 86 _4, 86 ₅ water channel 95 the

solid electrolyte

96, 97 Gas diffusion electrode layer 100 Carbon paper 102 Water repellent

Claims

Electrolysis of water supplied to the electrolyte by applying a voltage between the hydrogen side electrode and the oxygen side electrode, or the hydrogen side electrode, the electrolyte and the oxygen by the supplied hydrogen-containing gas and oxygen-containing gas A water electrolysis / fuel cell power generation cell that performs fuel cell power generation at a side electrode, comprising: an oxygen side electrode layer, an electrolyte layer, a hydrogen side electrode layer, and liquid water between the oxygen side electrode layer and the electrolyte layer A first gas separator that passes the separated oxygen-containing gas and a second gas separator that passes the hydrogen-containing gas separated from liquid water between the electrolyte layer and the hydrogen-side electrode layer are stacked. A cell stack portion provided with a catalyst layer between the oxygen side electrode layer and the electrolyte layer and / or between the electrolyte layer and the hydrogen side electrode layer;
A water flow path for supplying or discharging water in a first direction substantially perpendicular to the cell stacking direction;
An oxygen-containing gas flow path for discharging or supplying the oxygen-containing gas in a second direction substantially perpendicular to the stacking direction of the cells;
A hydrogen-containing gas flow path for discharging or supplying the hydrogen-containing gas in a third direction substantially perpendicular to the cell stacking direction;
With
A cell for water electrolysis / fuel cell power generation, wherein the oxygen side electrode layer and the hydrogen side electrode layer are water repellent electrode layers.
A plurality of slits are formed in the oxygen side electrode layer,
A plurality of grooves communicating with the water flow path are formed on one surface of the first gas separator,
The first gas separator and the oxygen side electrode are stacked, the plurality of grooves are aligned with the plurality of slits of the oxygen side electrode, and water from the water channel is electrolyzed when water is electrolyzed. The cell for water electrolysis / fuel cell power generation according to claim 1, wherein
A ladder-like member is formed between the plurality of slits of the oxygen side electrode layer,
At least one oxygen-side vent hole penetrating to the other surface and communicating with the oxygen-containing gas flow path is formed in the ladder-like portion other than the plurality of grooves of the first gas separator,
The oxygen-side vent hole is aligned with the ladder-shaped member of the oxygen-side electrode layer, and the oxygen-containing gas that has passed through the oxygen-side electrode layer during water electrolysis is circulated through the oxygen-containing gas flow path. Item 3. The water electrolysis / fuel cell power generation cell according to Item 1 or 2.
At least one hydrogen-side vent hole penetrating through the second gas separator and communicating with the hydrogen-containing gas flow path is formed,
The water electrolysis / fuel cell power generation cell according to any one of claims 1 to 3, wherein the hydrogen-containing gas that has passed through the hydrogen-side electrode layer is circulated through the hydrogen-containing gas flow path during water electrolysis.
Electrolysis of water supplied to the electrolyte by applying a voltage between the hydrogen side electrode and the oxygen side electrode, or the hydrogen side electrode, the electrolyte and the oxygen by the supplied hydrogen-containing gas and oxygen-containing gas A water electrolysis / fuel cell power generation cell that performs fuel cell power generation at a side electrode,
A first gas diffusion / separator, an oxygen side electrode layer held by the first gas diffusion / separator, an electrolyte layer and an electrolyte holding unit for holding the same, a hydrogen side electrode layer, a first for holding the hydrogen side electrode layer A cell stack portion in which two gas diffusion / separators are stacked and a catalyst layer is provided between the oxygen side electrode layer and the electrolyte layer and / or between the electrolyte layer and the hydrogen side electrode layer; ,
An oxygen-containing gas flow path provided in a second direction substantially perpendicular to the stacking direction of the first gas diffusion and separator;
A hydrogen-containing gas flow path provided in the third direction substantially perpendicular to the stacking direction and the second direction in the second gas diffusion and separator;
A water flow path provided in the electrolyte holding unit in a first direction substantially perpendicular to the stacking direction, supplying water from a side surface of the layer containing the electrolyte, or discharging water;
A cell for water electrolysis / fuel cell power generation, wherein the oxygen side electrode layer and the hydrogen side electrode layer are water repellent electrode layers.
The water electrolysis / fuel cell power generation cell according to any one of claims 1 to 5, wherein the electrolyte is a proton (H + ) conductive porous electrolyte and / or a dense electrolyte.
The water electrolysis / fuel cell power generation cell according to any one of claims 1 to 6, wherein one or both of the oxygen side electrode layer and the hydrogen side electrode layer comprises Teflon (registered trademark) modified porous carbon.
A cell laminate formed by laminating two or more cells according to any one of claims 1 to 7 in the laminating direction, wherein at least some of the water flow paths in each cell are connected to each other, At least a part of the oxygen flow path in each cell is connected to each other, at least a part of the hydrogen flow path in each cell is connected to each other, and at least a part of the oxygen-side electrode layer in each cell is electrically connected to each other. And at least part of the hydrogen-side electrode layers in each cell are electrically connected to each other.