JPH07220742A - Solid polymer electrolyte fuel cell and method for producing electrode-ion exchange membrane assembly of the fuel cell - Google Patents

Abstract

(57) [Summary] [Objective] The purpose is to prevent damage to the ion exchange membrane, which is a solid polymer of the electrolyte, without lowering the utilization rate of the catalyst layer. [Structure] The area of the ion exchange membrane 1 is made larger than the area of the gas diffusion electrode 4 composed of the catalyst layer 2 and the gas diffusion layer 3, and the peripheral portion of the ion exchange membrane 1 which is not joined to the gas diffusion electrode 4 is vertically arranged. A solid polymer electrolyte fuel cell configured to be sandwiched by gaskets 5. An ion exchange membrane 1 having a thin film thickness and a weak strength is provided by providing an auxiliary gasket 9 of a sealing material arranged at the periphery of the gas diffusion layer 3. Can be prevented without lowering the utilization rate of the catalyst layer 2.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid polymer electrolyte fuel cell (hereinafter referred to as a solid polymer electrolyte fuel cell using pure hydrogen as a fuel or a reducing agent such as reformed hydrogen from methanol and fossil fuels) and oxidizers such as air and oxygen. , Solid fuel cell) and a method for manufacturing an electrode-ion exchange membrane assembly of the fuel cell.

[0002]

2. Description of the Related Art A conventional solid fuel cell will be described below.

A solid fuel cell uses a cation exchange membrane, which is a proton conductor, as a solid polymer electrolyte, and when hydrogen is used as a fuel and oxygen is used as an oxidant, the chemical formula (1) is used at the negative electrode.
It is known that the reaction shown in (Chemical Formula 2) occurs at the positive electrode.

[0004]

[Chemical 1]

[0005]

[Chemical 2]

That is, in the negative electrode, hydrogen is dissociated into protons and electrons, the protons move in the cation exchange membrane toward the positive electrode, and the electrons are stacked in series with a conductive separator plate, and further in an external circuit. To reach the positive electrode,
At this time, power is generated. In the positive electrode, the protons that have moved in the cation exchange membrane, the electrons that have moved in the external circuit, and oxygen introduced from the outside react to generate water. Since this reaction is exothermic, hydrogen and oxygen generate electricity, water and heat as a whole.

The solid fuel cell differs from other fuel cells in that the electrolyte is composed of an ion exchange membrane which is a solid polymer. For this ion exchange membrane, a perfluorocarbon sulfonic acid membrane [made by du Pont (trade name: Nafion)] or the like is used, but the membrane is sufficient for showing sufficient proton conductivity. Must be hydrated. Means for hydrating the ion exchange membrane include, for example, Journal of of
Electrochem. Soc. 135 (198
8) As described in 2209, the reaction gas is passed through a humidifier to introduce water vapor into the cell to prevent the ion exchange membrane from drying.

Further, as a means for sealing each cell,
As shown in FIG. 5, the area of the ion exchange membrane 1 is made larger than the area of the gas diffusion electrode 4 composed of the catalyst layer 2 and the gas diffusion layer 3, and the periphery of the ion exchange membrane 1 which is not joined to the gas diffusion electrode 4 is surrounded. The part is sandwiched between the upper and lower gaskets 5.

As the material of the gasket 5, a glass fiber cloth coated with polytetrafluoroethylene (manufactured by DuPont, trade name Teflon) or fluororubber is used. In the figure, 6 is a ribbed porous electrode substrate, 7
Is a separator [eg Journal of
Power Sources, 29 (1990) 367
reference]. Silicone rubber and Viton rubber are also used for the gasket 5 (for example, US Patent, Pate).
nt No. 4,826,741).

In such a structure, the ion-exchange membrane 1 having a small thickness and weak strength was damaged at the end of the porous electrode substrate 6 and in the vicinity of the gasket 5.

As a means for preventing the ion exchange membrane 1 from being damaged, as shown in FIG. 6, a resin film 8 in which an ion exchange resin solution of a component of the ion exchange membrane 1 is applied to the bonding surface on the peripheral portion of the ion exchange membrane 1. Are bonded together by a hot press method to reinforce the ion exchange membrane 1, and the gas diffusion electrode 4 is connected to the ion exchange membrane 1.
Not only this, but also the resin film 8 is laid over and joined to prevent damage to the ion exchange membrane 1 (see, for example, Japanese Patent Laid-Open No. 174845/1993).

[0012]

However, in the above-mentioned conventional structure, since the resin film 8 of the insulator is sandwiched between the gas diffusion electrode 4 and the ion exchange film 1, the portion in contact with the resin film 8 Problem that the catalyst layer 2 does not work and the utilization rate decreases, and the cost is high because an expensive ion exchange resin solution is used for joining the ion exchange membrane 1 and the resin membrane 8. Had.

The present invention solves the above-mentioned conventional problems and prevents damage to the ion-exchange membrane, does not lower the utilization rate of the catalyst layer, and is a low-cost solid fuel cell and can be manufactured efficiently. It is an object of the present invention to provide a method for producing an electrode-ion exchange membrane assembly of the fuel cell.

[0014]

In order to achieve this object, the solid fuel cell of the present invention comprises an auxiliary gasket of a sealing material arranged at the periphery of the gas diffusion layer of the gas diffusion electrode. is there.

In the method for manufacturing the electrode-ion exchange membrane assembly of the fuel cell, the sealing material is applied so as to form the peripheral portion and the lattice-like portion and dried to form the auxiliary gasket on the gas diffusion layer. In this method, the electrode composite having the catalyst layer formed thereon is placed on both sides of the ion exchange membrane, joined by a hot pressing method, and then cut into a predetermined size.

[0016]

In this structure, the catalyst layer of the gas diffusion electrode is not wasted, and the ion exchange membrane is prevented from being damaged.

Also, in this method, a plurality of electrode-ion exchange membrane assemblies can be efficiently manufactured.

[0018]

【Example】

(Embodiment 1) Hereinafter, one embodiment of the solid fuel cell of the present invention will be described with reference to the drawings.

In one embodiment of the present invention, the same parts as those described in the above-mentioned conventional example are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 1, the feature of this embodiment lies in that in the conventional structure, instead of the resin film 8, an auxiliary gasket of a sealing material is provided around the gas diffusion layer 3 of the gas diffusion electrode 4. It is equipped with 9.

The ion exchange membrane 1 of this embodiment is composed of an ion exchange resin solution [Nafion solution, Aldrich Chemical,
(Manufactured by (Aldrich Chemical) Co., Ltd.), and the thickness dimension is 50 μm.

The auxiliary gasket 9 is made of ethylene tetrafluoride.
A sealant made of a copolymerized fluororubber of ethylene tetrafluoride and propion (Eight seal, Taihei Kasei Co., Ltd.) is applied and then dried to have a width of 2 mm.
The thickness is 10 mm and the thickness is 60 μm. The gas diffusion electrodes 4 each having the catalyst layer 2 formed on the gas diffusion layer 3 having the auxiliary gasket 9 are arranged on both sides of the ion exchange membrane 1 and joined by a hot pressing method to form an electrode-ion exchange membrane assembly.

As described above, according to the present embodiment, by providing the auxiliary gasket 9 of the sealing material provided on the periphery of the gas diffusion layer 3 of the gas diffusion electrode 4, the catalyst layer 2 is not wasted. Moreover, the ion exchange membrane 1 can be assembled without damage near the end of the porous electrode substrate 6 with ribs or the gasket 5.

Although the eight seals are used as the material of the auxiliary gasket 9 in this embodiment, the solid fuel cell is in contact with the ion exchange membrane 1 which is a strong acid, and the operating temperature of the solid fuel cell is 12
Since it is 0 ° C. or lower, any sealing material can be used as long as it is an insulating elastic material having acid resistance and heat resistance of 120 ° C. Further, the width dimension of the auxiliary gasket 9 differs depending on the shape of the separator 7 and is not limited to this embodiment. The thickness dimension of the auxiliary gasket 9 is a thickness dimension that can complement the thickness of the catalyst layer 2 of the gas diffusion electrode 4. The size is not limited to the size of this embodiment.

(Example 2) An example of a method for producing an electrode-ion exchange membrane assembly for a solid fuel cell of the present invention will be described below.

As shown in FIG. 2, a peripheral edge portion having a width dimension of 2 mm to 10 mm and a grid-shaped portion having a width dimension twice the width dimension of the peripheral edge portion are formed on one surface of the gas diffusion layer 3a similar to the first embodiment. As described above, the same sealing material as in Example 1 described above is applied and dried to form an auxiliary gasket 9a having a thickness of 60 μm, and then the catalyst layer 2a and the gas diffusion layer 3a provided with the auxiliary gasket 9a are formed. It is formed on the above and the electrode composite body 10a is produced. Then, as shown in FIG. 3, the ion-exchange membrane 1a is placed on both sides of the same ion exchange membrane 1a as in Example 1 and bonded by hot pressing to form an electrode-ion exchange membrane assembly, which is cut into a predetermined size. This makes it possible to efficiently manufacture a plurality of electrode-ion exchange membrane assemblies at the same time.

As shown in FIG. 4, the electrode composite body 10a described above is used.
The width is 2mm to 10mm on one side by the same manufacturing method as
Using the electrode composite body 10b in which the catalyst layer 2b is formed on the gas diffusion layer 3b provided with the auxiliary gasket 9b of the central rod-shaped portion having a size twice the width of the peripheral part and the width of the peripheral part.
The same effect can be obtained as an ion exchange membrane assembly.

As described in the first embodiment, the width dimensions and the thickness dimensions of the auxiliary gaskets 9a and 9b are not limited to the dimensions of this embodiment.

[0029]

As is apparent from the above description, the present invention prevents the ion exchange membrane from being damaged by the structure provided with the auxiliary gasket of the sealing material arranged at the periphery of the gas diffusion layer of the gas diffusion electrode. As a result, it is possible to realize an excellent solid fuel cell that does not lower the utilization rate of the catalyst layer and is low in cost.

Then, an electrode composite having a catalyst layer formed on a gas diffusion layer in which an auxiliary gasket is formed by applying a sealing material so as to form a peripheral portion and a lattice-like portion and drying the same on both sides of the ion exchange membrane. After being arranged and bonded by a hot pressing method, a method of cutting into a predetermined size by a method of efficiently manufacturing a plurality of electrode-ion exchange membrane assemblies of an excellent solid fuel cell electrode-ion exchange membrane assemblies The manufacturing method can be realized.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a solid polymer electrolyte fuel cell of Example 1 of the present invention.

FIG. 2 is a front view of an electrode composite used in a method for producing an electrode-ion exchange membrane assembly of a solid polymer electrolyte fuel cell according to Example 2 of the present invention.

FIG. 3 is a schematic sectional view of the electrode-ion exchange membrane assembly.

FIG. 4 is a front view of another electrode composite used in the method for producing the same electrode-ion exchange membrane assembly.

FIG. 5 is a schematic sectional view of a conventional solid polymer electrolyte fuel cell.

FIG. 6 is a schematic sectional view of another conventional solid polymer electrolyte fuel cell.

[Explanation of symbols]

 1, 1a Ion exchange membrane 2, 2a, 2b Catalyst layer 3, 3a, 3b Gas diffusion layer 4 Gas diffusion electrode 5 Gasket 9, 9a, 9b Auxiliary gasket 10a, 10b Electrode composite

Claims (2)

[Claims] 1. A solid polymer electrolyte fuel cell comprising an ion exchange membrane, a gas diffusion electrode disposed on both sides in contact with the ion exchange membrane, and a gasket, wherein a gas diffusion layer of the gas diffusion electrode is provided. A solid polymer electrolyte fuel cell, characterized in that an auxiliary gasket of a sealing material is provided around the periphery. 2. The method for producing a solid polymer electrolyte fuel cell according to claim 1, wherein a sealing material is applied so as to form a lattice portion and a peripheral portion, and dried to form an auxiliary gasket. Electrode composites with a catalyst layer formed on the diffusion layer are placed on both sides of the ion exchange membrane, bonded by hot pressing, and then cut to a predetermined size Electrode of solid polymer electrolyte fuel cell-ion exchange Method for manufacturing membrane assembly.