JPH06203849A - 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 together. CONSTITUTION:A catalyst having platinum supported to carbon black, a solvent solution of ion exchange resin such as perfluorocarbon sulfonate resin, and a diluting solvent are mixed together to form a suspension. The suspension is accumulated on an electrode base made water-repellent and is filtered through the electrode base while being dispersed, to take the platinum-supporting catalyst and the ion exchange resin in the suspension into the electrode base so as to form electrode sheets. Next, hot press is carried out with a film of ion exchange resin serving as a solid high polymer electrolyte film sandwiched between the two electrode sheets so that the electrode sheets and the film of ion exchange resin are bonded and integrated together. Manufacturing processes can thus be simplified without use of polytetrafluoroethylene.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing 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 by hot pressing at 210 kg / cm ² is disclosed. According to the method, an electrode reaction site is formed by mixing an ion exchange resin into an oxygen electrode integrally joined to a NAFION membrane as a solid electrolyte. 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% 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 a 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 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 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 suspension. In the suspension, the suspension is deposited on a water repellent-treated electrode base material, and then the suspension is filtered by an electrode base material while being preferably dispersed by pressure or suction. An electrode sheet is formed by incorporating the platinum-supported catalyst and the ion exchange resin in the electrode base material, and an ion exchange resin membrane as a solid polymer electrolyte membrane is sandwiched between the two electrode sheets and hot pressed. It is intended to provide a polymer electrolyte fuel cell characterized by joining and integrating the electrode sheet and the ion exchange resin membrane.

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 in the present invention, for example, NAFION-11.
7 (perfluorocarbon sulfonic acid resin, manufactured by DuPont, trade name). As a solvent solution of the ion exchange resin, an alcohol solution of NAFION-117,
Examples thereof include a mixed solvent solution of an aliphatic alcohol and water, and the concentration thereof is usually 0.1 to 5% by weight, preferably 1
Is in the range of up to 5% by weight.

The diluting solvent used in the present invention is
It is used to obtain a suspension, and examples thereof include a mixed solvent of an aliphatic alcohol and water, preferably i-propanol or a mixed solvent of 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. Homogeneous mixing is preferred, and this mixing forms a suspension.

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.
It is in the range of 00 to 400 parts by weight, preferably 350 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 in which catalyst particles do not exist is generated, which is not preferable. If the amount of the diluting solvent is less than 100 parts by weight per 100 parts by weight of the solvent solution of the ion exchange membrane, it is difficult to obtain a suspension, which is not preferable, and if it exceeds 400 parts by weight, the filtration described below takes too much time. It is not preferable in terms. Further, the amount of the diluent solvent is such that the solid content concentration of the slurry formed is 2.
The amount is in the range of 5 to 25% by weight, preferably 25 to 3% by weight, and if the solid content concentration of the slurry is less than 2.5% by weight, there is a problem that filtration takes too long, which will be described later. If it exceeds%, it is difficult to obtain a suspension, 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 is deposited in the range of mg / cm ² . When the amount of platinum is less than 0.01 mg / cm ² , the active sites of the catalyst are too small to allow a certain amount of current to flow, which is not preferable, and when it exceeds 4 mg / cm ² , the thickness of the reaction layer becomes large and the resistance becomes large. Is not preferable. Then, the deposited suspension is pressurized, or a negative pressure is applied to the side opposite to the suspension with respect to the electrode base material to suck the suspension, preferably using an ultrasonic homogenizer or the like. An electrode sheet is formed by filtering with an electrode base material while being dispersed and incorporating the platinum-supported catalyst and the ion exchange resin in the suspension into the electrode base material. If necessary,
The filtration is repeated until the platinum-supported catalyst and the ion exchange resin in the suspension are exhausted. Pressurization is performed here by, for example, a pressure filtration device, and suction is performed by, for example, a suction filtration device.

In this way, the solvent remaining in the applied electrode is evaporated and removed to form an electrode sheet. Evaporation and removal of the residual 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, there is an advantage that excellent battery performance can be obtained by a remarkably simplified manufacturing process, especially a large current can be obtained even at a low temperature, without using polytetrafluoroethylene in the prior art. A polymer electrolyte fuel cell is provided. According to the method of the present invention, when the suspension is filtered, the portion through which the filtrate has passed serves as a path for good mass transfer during operation of the electrode, and the solid polymer fuel has good mass transfer and high catalyst utilization rate. A battery electrode is obtained. According to the method of the present invention, when the suspension is filtered by pressurization or suction, it is carried out while dispersing the suspension, so that both the platinum-supported catalyst particles in the catalyst layer and the ion exchange resin as the solid polymer electrolyte are obtained. Are uniformly mixed, the utilization rate of the platinum-supported catalyst is improved, and the performance of the battery can be further improved.

[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 in which 40% by weight of platinum was supported on carbon black, 800 g of an alcohol solution of 5% by weight of Nafion 117 and 3200 g of a mixed solvent of water and alcohol in a weight ratio of 4: 1 was used. The mixture was uniformly mixed using an ultrasonic homogenizer to form a suspension having a solid content concentration of 3.5% 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 mm.
Of platinum on carbon paper of 4mg / cm
^Then , the suspension was filtered under a pressure difference of 200 kPa, and the platinum-supported catalyst and Nafion 117 in the suspension were taken into carbon paper to form an electrode sheet. N between the two formed electrode sheets
AFION117 membrane sandwiched, 150 ℃, 200kgf /
Pressed for 60 seconds under pressure of cm ² and electrode sheet and NAF
The ION-117 membrane is joined and integrated, and a current collector is adhered to both sides of the obtained joined body of the electrode sheet and the NAFION-117 membrane by a conventional method, and a hydrogen inlet and an oxygen inlet are provided to form a solid. A polymer fuel cell was obtained. Regarding the battery performance of the obtained battery, the hydrogen flow rate was 0.2.
Liter / min, normal pressure, oxygen flow rate 0.2 liter / m
When each gas was introduced into each electrode of each battery at in and normal pressure, the battery temperature was 60 ° C., the hydrogen gas was humidified, and a power generation test was performed. As a result, a current-voltage curve as shown in FIG. 1 was obtained.

Example 2 A polymer electrolyte fuel cell was obtained in the same manner as in Example 1 except that the deposited suspension was filtered while being dispersed by an ultrasonic homogenizer, and the same cell performance as in Example 1 was obtained. When the test was conducted, a current-voltage curve as shown in FIG. 1 was obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between voltage and current density in the performance of batteries obtained by a preferred embodiment of the method of the present invention, where 1 shows the results of Example 1 and 2 shows the results of Example 2.

Claims (5)

[Claims] 1. A catalyst in which platinum is 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 suspension, and the suspension is water-repellent. Of the platinum-supported catalyst and the ion exchange resin in the suspension by incorporating the platinum-supported catalyst and the ion-exchange resin in the suspension by depositing on the treated electrode base material and then filtering the suspension through the electrode base material by pressurization or suction. To form an electrode sheet,
A solid polymer, wherein an ion exchange resin membrane as a solid polymer electrolyte membrane is sandwiched between two electrode sheets and hot pressed to bond and integrate the electrode sheet and the ion exchange resin membrane. Type fuel cell manufacturing method. 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 the deposited suspension is in the range of 0.01 to 4 mg / cm ² , respectively, as the amount of platinum. 4. The filtration is repeated until the platinum-supported catalyst and the ion exchange resin in the suspension are exhausted.
The method described. 5. The method according to claim 1, wherein the filtering is performed while dispersing the deposited suspension.