JPH06203848A - Manufacture of solid high polymer fuel cell - Google Patents

Abstract

PURPOSE:To simplify manufacturing processes by performing hot press with a film of ion exchange resin sandwiched between two electrode sheets each formed from a specific slurry, for bonding and integrating the electrode sheets and the film of ion exchange resin to each other. CONSTITUTION:A catalyst having platinum supported to carbon black, a solvent solution of ion exchange resin such as perfluorocarbon sulfonate resin serving as solid electrolyte, and a diluting solvent are mixed together to form a slurry. The slurry is formed into a film on an electrode base which is made water- repellent by a method that uses polytetrafluoroethylene, etc. Next, the solvent contained in the slurry is vaporized and removed to form electrode sheets. Hot press is carried out with a film of ion exchange resin serving as solid high polymer electrolyte sandwiched between the two electrode sheets, for bonding and integrating the electrode sheets and the film of ion exchange resin to each other. Current collectors are brought into close contact with both sides of this stack to obtain a fuel cell. Manufacturing processes can thus be simplified without use of polytetrachloroethylene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polymer electrolyte fuel cell.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a polymer electrolyte fuel cell, electrode catalyst particles prepared in advance and polytetrafluoroethylene are mixed to form an electrode sheet, which is then used as an ion exchange resin membrane. There is known a method of thermocompression bonding to the above (for example, US Pat. Nos. 3,134,697 and 3297).
No. 484, No. 3432355). However, in the above method, the binding temperature of the electrode sheet is high, the thermocompression bonding with the ion exchange resin membrane cannot be performed at the same time, and the battery performance is not in a satisfactory state.

Further, as a method for producing a polymer electrolyte fuel cell, a method is known in which catalyst particles are deposited by chemical reduction near the surface in the ion exchange resin membrane (for example,
Japanese Patent Publication No. 58-47471). However, the above method has a drawback in that the catalyst exists in the ion exchange resin as fine particles as much as possible, in other words, exists in a highly dispersed state, and it is difficult for the fine particles to maintain electrical contact with each other.

Electrochemistry, 53, No. 10 (198
5), pp. 812-817, carbon powder carrying 10% platinum was used as the electrode catalyst powder for the oxygen electrode, and NAFION-117 (perfluorocarbon sulfonic acid resin, manufactured by DuPont, (Trade name) solution, that is, a mixed solvent solution of 5% concentration of NAFION-117 in aliphatic alcohol and water is mixed at various mixing ratios, and 60% of PTFE is added in the form of an aqueous suspension to obtain a mixture. After kneading, it is rolled into a sheet, and the oxygen electrode sheet obtained by vacuum drying is applied to a NAFION membrane (manufactured by DuPont, solid polymer electrolyte membrane, trade name) at 100 ° C.
A method for joining oxygen electrodes that is hot pressed at 210 kg / cm ² is disclosed. According to the method, an ion exchange resin is mixed into an oxygen electrode that is integrally joined to a NAFION membrane as a solid electrolyte so that an electrode reaction site is formed. It has been reported that the polarization characteristics are remarkably improved when the three-dimensional structure is attempted. However, in the above method, since PTFE is used, the battery performance is not sufficient, and the kneading / rolling process is used, so the manufacturing process of the electrode sheet is complicated.

Japanese Unexamined Patent Publication No. 4-162365 discloses 30
Carbon black supporting wt% of platinum was immersed in a solution of NAFION in butanol, and then vacuum-dried to prepare catalyst fine particles with Nafion on the surface, and non-catalyst carbon black prepared separately was used. Of non-catalyst fine particles having Nafion added to the surface thereof, and then a mixture of these two kinds of fine particles is mixed with polytetrachloroethylene (PTFE) dispersion, followed by filtration and drying, The obtained mixture fine powder is usually used as a fuel cell electrode base material, and contains 20 wt% P
Platinum was sprayed onto TFE water repellent carbon paper so that the weight of platinum was 0.5 mg / cm ^2, and then 1
An electrode is formed by pressing at 30 ° C. under a pressure of 40 kg / cm ² for 5 seconds, an ion exchange resin membrane Nafion 117 is sandwiched between the two electrodes, and 160 ° C. under a pressure of 40 kg / cm ² for 5 seconds. A method for producing an electrode for a fuel cell, which comprises pressing and integrating, is disclosed. According to the method, a high-performance electrode and a low-cost electrode can be easily obtained with a small amount of a catalyst, and a small size and high power density can be obtained. It is described that it is possible to produce the fuel cell of. However, the above method has a drawback that the manufacturing process is extremely complicated, and further, there is a problem in the formability of the electrode because the heat treatment is not performed at a temperature of 360 ° C. or higher at which PTFE is bound.

An object of the present invention is to provide a solid polymer electrolyte fuel cell which has excellent cell performance in a significantly simplified manufacturing process without using polytetrachloroethylene in the prior art.

[0007]

According to the present invention, a catalyst prepared by supporting platinum on carbon black, a solvent solution of an ion exchange resin as a solid polymer electrolyte, and a diluting solvent are mixed to form a slurry. The slurry is applied on the water-repellent electrode base material in a film form, the solvent contained in the slurry is evaporated and removed to form an electrode sheet, and a solid polymer is provided between the two electrode sheets. The polymer electrolyte fuel cell is characterized in that the electrode sheet and the ion-exchange resin membrane are joined and integrated by hot pressing with an ion-exchange resin membrane as an electrolyte membrane sandwiched therebetween.

In the present invention, the amount of platinum supported on the catalyst in which platinum is supported on carbon black is usually 5 to 40% by weight, preferably 25 to 40% by weight.

As an example of the ion exchange resin as the solid polymer electrolyte membrane in the present invention, for example, NAFION-1
17 (perfluorocarbon sulfonic acid resin, manufactured by DuPont, trade name). Examples of the solvent solution of the ion exchange resin include an alcohol solution of NAFION-117, a mixed solvent solution of an aliphatic alcohol and water, and the concentration thereof is usually 0.1 to 5% by weight, preferably 1 to 5%. It is in the range of% by weight.

The diluting solvent used in the present invention is
It is used for homogenizing the slurry, and examples thereof include a mixed solvent of an aliphatic alcohol and water, preferably a mixed solvent of i-propanol or n-butanol and water.

In the present invention, the method of mixing the platinum-supported catalyst, the solvent solution of the ion exchange resin and the solvent for dilution is not particularly limited in the order of mixing and they may be mixed at the same time, for example, using an ultrasonic homogenizer. It is preferable to mix uniformly, and this mixing forms a slurry.

In the present invention, the mixing ratio of the platinum-supported catalyst, the solvent solution of the ion exchange resin and the diluting solvent is such that the amount of the solvent solution of the ion exchange resin is 5 to 100 parts by weight of the catalyst as the ion exchange resin. It is in the range of 50 parts by weight, preferably 10 to 50 parts by weight, and the amount of the diluted solvent is 1 per 100 parts by weight of the solvent solution of the ion exchange resin.
The amount is in the range of 00 to 400 parts by weight, preferably 200 to 400 parts by weight. When the amount of the solvent solution of the ion exchange resin is less than 5 parts by weight per 100 parts by weight of the catalyst as the ion exchange resin, the resin does not sufficiently reach the catalyst particles, which is not preferable in terms of film-forming property. If it exceeds the above range, a portion of the ion exchange membrane having no catalyst particles is generated, which is not preferable. The amount of the diluting solvent is 1 per 100 parts by weight of the solvent solution of the ion exchange membrane.
If it is less than 00 parts by weight, it is difficult to obtain a uniform slurry, which is not preferable, and if it exceeds 400 parts by weight, it takes a long time to evaporate and remove the solvent described later, which is not preferable. Further, the amount of the diluting solvent is such that the solid content concentration of the slurry formed is in the range of 2.5 to 25% by weight, preferably 5 to 25% by weight, and the solid content concentration of the slurry is 2. If it is less than 5% by weight, it takes a long time to evaporate and remove the solvent described later, and if it exceeds 5% by weight, it is difficult to obtain a uniform slurry, which is not preferable.

The slurry thus formed has a platinum content of 0.01 to 4 on the water-repellent electrode base material.
Each film is applied in the range of mg / cm ² . If the amount of platinum is less than 0.01 mg / cm ² , the number of active sites of the catalyst is too small to pass a current of a certain amount or more, which is not preferable, and if it exceeds 4 mg / cm ² , the thickness of the reaction layer increases and the resistance increases. It is not preferable because it becomes large. As the electrode base material, a conventionally known material such as carbon paper can be used, and the carbon paper having a porosity of 50 to 90%, preferably 70 to 80% can be used. The water repellent treatment of the electrode base material is, for example, PT
It can be carried out by a known method using FE (polytetrafluoroethylene). Examples of the method for applying the slurry on the electrode base material include various conventionally known coating methods, printing methods, doctor blade methods and the like.

In this way, the solvent contained in the slurry applied on the electrode substrate is evaporated and removed to form the electrode sheet. Evaporation / removal of the solvent can be performed by vacuum drying at 80 ° C., for example.

Next, an ion exchange resin membrane as a solid polymer electrolyte membrane is sandwiched between the two electrode sheets thus formed and hot pressed to join and integrate the electrode sheet and the ion exchange resin membrane. To do. This hot press
Normal temperature 140 ~ 200 ℃, pressure 25 ~ 200kgf /
It can be carried out under pressure conditions of cm ² and pressing time of 3 to 180 seconds.

A solid polymer fuel is prepared by bringing a current collector into close contact with both sides of the thus formed bonded body of the ion exchange resin membrane and the electrode sheet by a conventional method, and further providing a hydrogen inlet / outlet and an oxygen inlet / outlet. You can get a battery.

[0017]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain excellent battery performance in a significantly simplified manufacturing process, particularly to obtain a large current even at a relatively low temperature, without using polytetrachloroethylene in the prior art. A polymer electrolyte fuel cell is provided.

[0018]

The present invention will be described in more detail with reference to the following examples.

Example 1 A mixture of 100 g of a catalyst comprising 40% by weight of platinum supported on carbon black, 800 g of an alcohol solution of 5% by weight of Nafion 117 and 1600 g of a mixed solvent of water and alcohol in a weight ratio of 1: 4 was prepared. The mixture was uniformly mixed using an ultrasonic homogenizer to form a slurry having a solid content concentration of 5.8% by weight. Water-repellent treatment was performed by a conventional method using a 25 wt% PTFE solution, and the porosity was 75% and the thickness was 0.4 m.
The amount of platinum on the carbon paper of m is 4 mg /
It was evenly applied to have a size of cm ^2, and the solvent was evaporated and removed by vacuum drying to form an electrode sheet. NAFION-117 film is sandwiched between two formed electrode sheets, and 1
The electrode sheet and the NAFION-117 membrane are joined and integrated by pressing at 50 ° C. under a pressure of 200 kgf / cm ² for 60 seconds, and both surfaces of the obtained joined body of the electrode sheet and the NAFION-117 membrane are coated by a conventional method. A solid polymer fuel cell was obtained by bringing the current collector into close contact and further providing a hydrogen inlet / outlet and an oxygen inlet / outlet. Hydrogen and oxygen were introduced into both electrodes of the obtained battery at normal pressure in an amount of 0.2 liters per minute, the temperature of the battery was kept at 60 ° C., and the hydrogen gas was humidified. Power generation was confirmed for several hours or more under the condition of 5 amps.

Claims (3)

[Claims] 1. A catalyst comprising platinum supported on carbon black, a solvent solution of an ion exchange resin as a solid polymer electrolyte, and a diluting solvent are mixed to form a slurry,
The slurry is applied in a film form on the water-repellent-treated electrode base material, the solvent contained in the slurry is evaporated and removed to form an electrode sheet, and the solid sheet is placed between the two electrode sheets. The ion exchange resin membrane as a molecular electrolyte membrane is sandwiched and hot pressed to join the electrode sheet and the ion exchange resin membrane.
A method for manufacturing a polymer electrolyte fuel cell, characterized by being integrated. 2. The amount of the solvent solution of the ion exchange resin is in the range of 5 to 50 parts by weight per 100 parts by weight of the catalyst as the ion exchange resin, and the amount of the diluted solvent is the solvent solution of the ion exchange resin. It is in the range of 100 to 400 parts by weight per 100 parts by weight, and the solid content concentration of the slurry is 2.5 to 25.
The method of claim 1 in the range of weight percent. 3. The method according to claim 1, wherein the amount of slurry applied is in the range of 0.01 to 4 mg / cm ² as the amount of platinum.