JPH08148167A - Bonding body of polymer electrolyte membrane and electrode and bonding method thereof - Google Patents

Abstract

(57) [Summary] [Structure] A gas diffusion electrode is placed on the polymer electrolyte membrane, and a solvent capable of dissolving the electrolyte membrane is impregnated from the gas diffusion layer of the electrode to impregnate the surface where the membrane and the electrode are in contact with each other. A joined body of a polymer electrolyte membrane for a fuel cell and an electrode, which comprises removing the solvent after dissolving the surface of the membrane, and a joining method thereof. [Effect] The joined body of the polymer electrolyte membrane and the electrode produced by the joining method of the present invention adheres because the membrane is dissolved and re-membraned at the contact surface between the polymer electrolyte membrane and the electrode. A strong bonded body can be obtained. Further, since pressing is not performed unlike the conventional method, it is possible to prevent the polymer electrolyte membrane and the electrode from being damaged without applying unnecessary force to the membrane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joined body of a polymer electrolyte membrane and an electrode in a polymer electrolyte fuel cell and a joining method thereof, and more specifically, it has excellent adhesion and The present invention relates to a joined body of a polymer electrolyte membrane and an electrode for a polymer electrolyte fuel cell, which has excellent adhesion without damaging the electrolyte membrane and the electrode, and a joining method thereof.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell is characterized in that an ionic conductor, that is, an electrolyte, is a solid and a polymer. A membrane such as a resin is used, and both the negative electrode and the positive electrode are arranged with the polymer electrolyte membrane sandwiched therebetween. For example, by supplying hydrogen to the negative electrode side and oxygen or air to the positive electrode side, an electrochemical reaction is performed. It wakes up and generates electricity.

The polymer electrolyte membrane has been improved and improved from the initial condensation synthetic membrane of phenol sulfonic acid and formaldehyde, and since then, it has been partially sulfonated polystyrene membrane and styrene-divinylbenzene as fluorocarbon. After cross-linking to the Bonn matrix, the sulfonation membrane,
There are proposed a film containing no -H bond, a polymer film of trifluorostyrene sulfonic acid, a film obtained by grafting trifluoroethylene on a fluorocarbon matrix, a perfluorocarbon sulfonic acid film, and the like.

Among these, the perfluorocarbon sulfonic acid film (trade name, NAFION) has excellent electrical characteristics, in addition to [ionic conductivity 5 × 10 ⁻² S · cm ⁻¹ (wet condition, 25 ° C.). )], It is extremely stable both chemically and physically and has a large mechanical strength. This film has a thickness of 50-200
It is used as a film of about μm, and the electric resistance per unit area is 0.1 to 0.5 Ω, which is so small that it cannot be the main cause of the internal resistance of the battery.

On the other hand, as both the negative electrode and the positive electrode in contact with the solid polymer electrolyte membrane, a type in which catalyst particles for promoting the reaction are added to the electrodes has been developed. As described above, various methods have been proposed so far for manufacturing an electrode in which a catalyst is added to and used in the electrode. As one of the systems, the catalyst particles are further mixed with polytetrafluoroethylene. The form is known.

For example, in US Pat. No. 3,297,484, catalyst particles such as platinum black and palladium black, or a kneaded product obtained by mixing catalyst particles in which these are supported on carbon particles with polytetrafluoroethylene is used as an electrode sheet.
And a method of thermocompression-bonding this to an ion exchange resin membrane as a polymer electrolyte, and in US Pat. No. 3,432,355, the kneaded product is separately applied as a slurry on a film of polytetrafluoroethylene. A method has been proposed in which an electrode sheet is used, and this is thermocompression-bonded to an ion exchange resin membrane as a polymer electrolyte.

In this technique, such mixing of polytetrafluoroethylene with the catalyst particles is mainly to bind the catalyst components forming the catalyst layer in the electrode sheet,
Although it is for binding, the reaction site (reaction region) is limited to a two-dimensional interface between the two by just joining the polymer electrolyte and the electrode sheet in this way, and The working area is small. Therefore, as one of the methods for improving this point, a carbon powder carrying a catalytic metal, a styrene-divinyl sulfonic acid resin powder, and a polystyrene binder are added to a styrene-divinyl benzene sulfonic acid resin membrane as a solid electrolyte. It has been proposed that the number of contact points between the electrode material and the solid polymer electrolyte be increased by joining the electron-ion mixed conductor layers made of the mixture to increase the number of reaction sites in three dimensions.

"Electrochemistry" 53, No. 10 (198
5), P. 812 to 817, the above three-dimensionalization technique is introduced, and in such a polymer electrolyte fuel cell using a styrene-divinylbenzene ion exchange resin membrane as an electrolyte, an electron-ion mixed conductor layer is provided. even if,
After pointing out that there are problems such as low current density that can be taken out, an attempt to increase the working area by introducing three-dimensional reaction sites was introduced in the case of using an alternative perfluorocarbon sulfonic acid resin film. ing.

According to this, NA which is a kind of perfluorocarbon sulfonic acid resin membrane as the solid polymer electrolyte.
A FION film is used, and a platinum electrode is bonded to one surface of the NAFION film by an electroless plating method (permeation method) to form a hydrogen electrode, that is, an anode side electrode. The negative electrode is manufactured by the following steps.

First, platinum black powder or carbon powder carrying 10% platinum (hereinafter referred to as "platinum-supporting carbon powder") was used as an electrode catalyst powder for oxygen electrode, and Amberlite IR was added to this. -120B (T-3) [styrene-divinylbenzenesulfonic acid resin, Na type, particle size 3
0 μm powder, manufactured by Organo, trade name) or NAF
ION-117 [perfluorocarbonsulfonic acid resin (H type), 5% solution in a mixed solvent of aliphatic alcohol and water, manufactured by Aldrich Chemical Co., trade name]
Are mixed in various mixing ratios.

Then, to each of the above mixtures, polytetrafluoroethylene was added in the form of an aqueous suspension, in the case of platinum black powder, 30% by weight of solid content, and in the case of platinum-supporting carbon powder, 60% was also added. After kneading, the kneaded product is rolled into a sheet, vacuum dried, and the oxygen electrode sheet is hot at a temperature of 100 ° C. and a pressure of 210 kg / cm ² with respect to the NAFION membrane as a solid polymer electrolyte. It is to press.

According to this, by mixing the ion exchange resin into the oxygen electrode integrally bonded to the NAFION membrane as the solid polymer electrolyte, the three-dimensionalization of the electrode reaction site is achieved. It is pointed out that the polarization characteristics can be remarkably improved, and that the effect of mixing the ion exchange resin is particularly large when the platinum-supporting carbon is used as the electrode catalyst. And here, the catalyst particles composed of platinum black powder or platinum-supported carbon powder,
It is coated with a polymer electrolyte mixed therein, and the above-mentioned "platinum black powder has a solid content of 30% by weight, and platinum-supported carbon powder has the same amount of 6%.
Polytetrafluoroethylene added in a proportion of 0% corresponds to the binder.

In the above technique, all the electrode sheets are produced by forming a kneaded product of the electrode material into a sheet by rolling or the like (in the case of US Pat. No. 3,432,355, an auxiliary film). As a mode of producing this electrode sheet, that is, a method of forming a sheet, a porous paper or sheet is used as a base material, and a catalyst such as catalyst particles is used. A method of supporting the layer-forming component is also used. In this case, as the paper or sheet, for example, a car having a predetermined porosity and thickness.
Using a bomber, impregnating it with a polytetrafluoroethylene-based dispersion, followed by heat treatment,
An electrode constituent component such as catalyst particles is attached and carried on the water repellent carbon paper, and one example thereof is Japanese Patent Publication No. 4-162365.

The technique of this publication is characterized in that a mixture of carbon black supporting a platinum catalyst and carbon black not supporting a catalyst is used as the fine powder for the catalyst layer constituting the electrode sheet. However, a water-repellent carbon paper is used for the sheet formation, and a mixture of fine powder containing catalyst particles is sprayed onto the water-repellent carbon paper and heated. It is adhered by pressing below, and the subsequent adhesion between the sheet-like catalyst layer and the ion-exchange resin membrane is performed by thermocompression bonding, and this thermocompression bonding is specifically performed at a temperature of 160 ° C. It is carried out at a pressure of 50 kg / cm ² .

Here again, these catalyst particles are coated with an ion exchange resin and treated with polytetrafluoroethylene. However, the present inventor has simplified the manufacturing process without using polytetrafluoroethylene, We have separately developed a method for manufacturing electrodes for polymer electrolyte fuel cells that have excellent cell performance, and have filed a patent application earlier (Japanese Patent Application No.
No. 358058, Japanese Patent Application No. 4-358059), and also in this case, there is no difference in using such a water-repellent carbon paper as the base sheet, and an ion exchange resin membrane. For example, the temperature is 150 ° C and the pressure is 1
Pressing is performed at 00 kgf / cm ² for 60 seconds.

As described above, the positive and negative electrodes themselves have been improved by including the three-dimensionalization of the contact surface with the polymer electrolyte membrane,
Even if devised, both positive and negative electrodes need to be bonded to the polymer electrolyte membrane, but this requires high temperature (140 ~
It is indispensable to perform thermocompression bonding by applying a high pressure (200 to 200 ° C.) and high pressure (50 to 200 kg / cm ² ), and therefore, unnecessary force is applied to the polymer electrolyte membrane and both electrodes.
It was unavoidable to damage the electrolyte membrane at the time of joining them.

[0017]

In view of such problems in the prior art of joining both electrodes to a polymer electrolyte membrane, the present inventor has proposed a method of joining the polymer electrolyte membrane and both positive and negative electrodes. , While conducting diligent experiments and devising methods that can be performed without damaging the electrolyte membrane, the bonding surface is dissolved by using a specific solvent, and the bonding is performed without the need for temperature and pressure. The inventors have come up with the present invention by devising and developing a method capable of doing so.

That is, according to the present invention, when the polymer electrolyte membrane and the gas diffusion electrode in the fuel cell are joined, the gas diffusion layer of the electrode is impregnated with a solution capable of dissolving the electrolyte membrane, thereby It is an object of the present invention to provide a method for joining a polymer electrolyte membrane and an electrode, which can be joined without requiring temperature and pressure for joining, and thus without causing damage to the membrane, and to obtain the same. Another object of the present invention is to provide a joined body of a polymer electrolyte membrane and an electrode.

[0019]

According to the present invention, a polymer electrolyte membrane and a gas diffusion electrode are impregnated with a solvent capable of dissolving the electrolyte membrane from a gas diffusion layer of the electrode, and The present invention provides a joined body of a polymer electrolyte membrane for a fuel cell and an electrode, which is obtained by dissolving the surface of the membrane and then removing the solvent.

Further, according to the present invention, in joining the polymer electrolyte membrane and the gas diffusion electrode, the gas diffusion layer of the electrode is impregnated with a solvent capable of dissolving the electrolyte membrane, whereby the polymer electrolyte membrane and the electrode are The present invention provides a method for joining a polymer electrolyte membrane for a fuel cell and an electrode, characterized in that the solvent is removed after the surface of the membrane that is in contact with is dissolved.

In the present invention, the solvent is used to dissolve and re-form the polymer electrolyte membrane component at the contact surface between the electrode and the polymer electrolyte membrane, whereby a bonded body having strong adhesion can be obtained. The solvent is not particularly limited as long as it can dissolve and re-form the electrolyte membrane from the gas diffusion layer of the electrode, and can bond the both by the dissolved membrane. -Rules can be used. When this is an alcohol, a lower alcohol, especially ethanol, which can dissolve the membrane, is preferable.

The present invention will be described in more detail below.
FIG. 1 is a schematic diagram for explaining the principle and basic operation of the present invention. In FIG. 1, reference numeral 1 is a polymer electrolyte membrane, which is placed on an appropriate table. Reference numeral 2 is a sheet electrode, 3 is a gas diffusion layer of the sheet electrode 2, and 4 is a catalyst layer of the electrode 2. The sheet-shaped electrode 2 is placed on the polymer electrolyte membrane 1 so that the catalyst layer 4 is in contact therewith as shown in the figure.

Next, for this bonding operation, a solvent such as alcohol is applied on the surface of the gas diffusion layer. This coating can be performed by an appropriate method such as spraying or dropping, but in order to prevent the solvent from flowing out from the peripheral portion of the gas diffusion surface, a mask or a weir is provided on the peripheral portion as needed. Is desirable. The solvent is applied in this manner, and a predetermined amount of the solvent is impregnated from the gas diffusion layer side, and then dried at room temperature, during which the polymer substance on the surface of the polymer electrolyte membrane is dissolved by the solvent, and this dissolved substance is It acts as a bonding agent and the catalyst layer surface is bonded to the polymer electrolyte membrane surface.

Further, one mode of this joining operation will be described. (1) A gas diffusion electrode is formed on a polymer electrolyte membrane such as Nafion 117 (trade name, manufactured by DuPont) so that the catalyst layer is in contact with the electrolyte membrane. Let (2) On the surface of the electrode on the gas diffusion layer (opposite side of the catalyst layer) side, a solvent that can serve as a solvent for the polymer electrolyte membrane, for example, an aqueous ethanol solution is added.
Apply evenly at a rate of 1 to 10 mg / cm ² . (3) After being impregnated with ethanol on the gas diffusion layer so that it is no longer visible to the naked eye, it is dried at room temperature for about 10 to 60 minutes.

(4) Next, the dried joined body is put into water and ultrasonic waves are applied to completely remove the remaining solvent, thereby obtaining a joined body of the electrode and the membrane. In this case, vacuum drying may be used as a method for removing the residual solvent.
(5) Further, electrodes are bonded to both sides of the polymer electrolyte membrane, but (4)
After the operation of (3) is completed, they can be joined in the same manner as in the above (1) to (4).

[0026]

EXAMPLES Examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these examples. First,
Catalyst particles were prepared by supporting platinum in a beaker (volume: 1 liter) at a ratio of 50% by weight with respect to carbon black particles, and the amount of the catalyst particles was 20% by weight based on the total amount of the particles. An alcohol solution of NAFION-117 (a perfluorocarbon sulfonic acid resin, manufactured by Du Pont, trade name) was added and uniformly mixed.

Next, the solvent was removed from this mixed solution. In this operation, the solvent was removed by evaporating by heating to a temperature of 50 ° C. with stirring and sucking with an aspirator to lower the pressure in the container. The solvent was carried out in a so-called flow-through mode in which it was cooled by a cooler connected to the discharge conduit, and the condensed solvent was stored in another container. Subsequently, a dispersion of polyflon (polytetrafluoroethylene, manufactured by Daikin Industries, Ltd., registered trademark) was added to and mixed with the coating catalyst particles thus obtained to uniformly disperse the catalyst particles and polytetrafluoroethylene. An aqueous suspension in which the coating catalyst particles were uniformly dispersed was obtained.

On the other hand, a carbon paper having a porosity of 80% and a thickness of 0.4 mm was impregnated with a dispersion of NEOFLON (tetrafluoroethylene-hexafluoropropylene copolymer, manufactured by Daikin Industries, Ltd., registered trademark). After heat treatment, carbon paper made water repellent with NEOFLON
I got In this case, the quantitative ratio was adjusted so that neofuron accounted for 20% by weight in the total amount. Next, the suspension of the catalyst particles obtained in (1) was filtered on the water repellent carbon paper obtained above, and each coated catalyst particle was placed on the water repellent carbon paper. Was uniformly deposited. The filtration operation was carried out by placing a water-repellent carbon paper on a perforated plate, pouring the suspension onto the porous plate, while pressing the upper part to allow only the solvent to permeate.

The layer deposited on the above water repellent carbon paper is the catalyst layer, and the NAFION-11 as a kind of solid polymer electrolyte is continuously applied to the adhering surface.
7 [perfluorocarbon sulfonic acid resin (H type), 5% solution in a mixed solvent of alcohol and water, Aldrich
Chemical Co., Ltd. product name] alcohol solution was sprayed, and the catalyst layer was impregnated with the solution to 4 mg / cm ² and then heated under reduced pressure at a temperature of 80 ° C. for 3 hours to remove the solvent and use an electrolyte. A coated electrode was obtained, which is a gas diffusion electrode 1 having a gas diffusion layer 3 and a catalyst layer 4 as shown in FIG.

Next, Nafion 117 prepared in advance is used.
On the membrane (polymer electrolyte membrane, manufactured by Du Pont, trade name), the gas diffusion electrode 1 obtained above was placed on the catalyst layer 4 as shown in FIG.
Is placed in contact with the electrolyte membrane 1 and 0.5 mg / cm of ethanol is applied to the surface on the gas diffusion layer (opposite side of the catalyst layer) side.
^It was evenly applied so as to have a thickness of ^2, and was impregnated with ethanol on the gas diffusion layer so that it could not be visually recognized, and then dried at room temperature for 30 minutes. Subsequently, the dried joined body is placed in water and ultrasonic waves are applied thereto to remove residual alcohol.
Completely removed to obtain a joined body of the polymer electrolyte membrane and the electrode. Also, for the other surface of the polymer electrolyte membrane,
The gas diffusion electrodes were joined in the same manner as above.

Visual observation of the joined body of the electrode and the polymer electrolyte membrane film revealed that the polymer electrolyte membrane and the electrode were closely adhered to each other, and no pressing was performed. In some cases, no damage to the membrane due to bonding was observed. Moreover, even if they were separated, they were not separated.

[0032]

As described above, the polymer electrolyte membrane-electrode assembly produced by the bonding method of the present invention has the membrane dissolved and re-membraned at the contact surface between the polymer electrolyte membrane and the electrode. By doing so, a bonded body having strong adhesion can be obtained. Further, since pressing is not performed unlike the conventional method, it is possible to prevent the polymer electrolyte membrane and the electrode from being damaged without applying unnecessary force to the membrane.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the principle and operation of the present invention.

[Explanation of symbols]

 1 Polymer Electrolyte Membrane 2 Electrode 3 Gas Diffusion Layer 4 Catalyst Layer

Claims (6)

[Claims] 1. A joined body of a polymer electrolyte membrane and a gas diffusion electrode, wherein a gas diffusion layer of the electrode is impregnated with a solvent capable of dissolving the electrolyte membrane, and A joined body of a polymer electrolyte membrane for a fuel cell and an electrode, which is obtained by dissolving the surface and then removing the solvent. 2. The gas diffusion electrode according to claim 1, wherein the catalyst layer comprising a mixture of catalyst particles, a polymer electrolyte and polytetrafluoroethylene is formed on a water repellent carbon paper. A joined body of the polymer electrolyte membrane for a fuel cell described above and an electrode. 3. The assembly of a polymer electrolyte membrane for a fuel cell and an electrode according to claim 1, wherein the solvent is an ethanol aqueous solution. 4. When joining a polymer electrolyte membrane and a gas diffusion electrode, an alcohol solution capable of dissolving the electrolyte membrane is impregnated from the gas diffusion layer side of the electrode to bring the polymer electrolyte membrane into contact with the electrode. A method for joining a polymer electrolyte membrane for a fuel cell and an electrode, which comprises dissolving the surface of the surface membrane and then removing the solvent. 5. The gas diffusion electrode according to claim 4, wherein the catalyst layer composed of a mixture of catalyst particles, a polymer electrolyte and polytetrafluoroethylene is formed on a water repellent carbon paper. A method for joining a polymer electrolyte membrane for a fuel cell described above and an electrode. 6. The method for joining a polymer electrolyte membrane for a fuel cell and an electrode according to claim 4, wherein the solvent is an aqueous solution of ethanol.