JP3229025B2 - Gas diffusion electrode manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a solid polymer electrolyte type electrolytic cell, in particular, a gas diffusion electrode used for a fuel cell.

[0002]

2. Description of the Related Art As a conventional method for producing a gas diffusion electrode for a solid polymer electrolyte fuel cell, a solvent is blended with a raw material powder of a reaction layer composed of hydrophilic and hydrophobic carbon black and polytetrafluoroethylene and rolled. Sheet molded,
There is a laminate obtained by mixing a solvent naphtha with a raw material powder of a diffusion layer composed of hydrophobic carbon black and polytetrafluoroethylene, forming a rolled sheet, and further rolling the sheet repeatedly to form a sheet.

[0003]

A conventional method for manufacturing a gas diffusion electrode is to repeat rolling by adding a solvent naphtha as a solvent to carbon black or a mixture of hydrophilic and hydrophobic carbon black and polytetrafluoroethylene and using a roll or the like. There is a problem that the gas diffusion path is crushed to form a sheet, the gas diffusion property is reduced, and the performance of the fuel cell is reduced.

Therefore, in order to increase gas diffusivity on the reaction layer side on which the catalyst is supported, attempts have been made to reduce the thickness of the reaction layer as much as possible. Since the number of times of rolling increases, the number of gas diffusion paths decreases, and the effect is small. Also, on the diffusion layer side, the gas passage is crushed by repeated rolling, and the gas diffusivity is reduced, so that there is a disadvantage that the limiting current due to gas diffusion resistance is small.

[0005] Such gas diffusivity has a small effect on the hydrogen supply side, which is the fuel electrode, because the hydrogen diffusivity is large. The performance of the battery is significantly affected by the necessity of discharging the battery.

The present invention has been made in view of the above-mentioned state of the art, and has as its object to provide a method for manufacturing a gas diffusion electrode free from defects as in the prior art.

[0007]

Means for Solving the Problems The present invention, in advance, hydrophilic carbon black, a reaction layer material powder of hydrophobic carbon black and polytetrafluoroethylene, a hydrophobic carbon black and polytetrafluoroethylene Diffusion layer raw material powder is prepared, and the above reaction layer raw material powder or
Goldenrod raw material powder sprinkled through a sieve, porous carbon thereon
Place the base material, and further place the diffusion layer raw material powder on it
Alternatively , a method for producing a gas diffusion electrode, comprising sprinkling a raw material powder for a reaction layer through a sieve, forming the whole in a cold state , and then sintering by hot pressing .

[0008]

By using a porous carbonaceous substrate such as carbon fiber woven fabric, carbon paper, or porous carbon as a substrate, a sufficient gas passage is ensured. In addition, since both the reaction layer and the diffusion layer have not been subjected to the repetitive stretching process such as the roll method, each of the layers has a porous gas diffusion path, and is used for a solid polymer electrolyte fuel cell. In this case, the current density per unit area is significantly increased due to the removal of reaction water and the improvement of gas diffusivity.

[0009]

【Example】

(Example) A plain weave 1K (K is the number of filaments in the properties of carbon fiber, K = 1000) carbon fiber fabric as a base material, and hydrophilic carbon black (Vulcan XC-72R:
A reaction layer raw material powder obtained by mixing and drying 35% of Cabot Corporation (trade name), 35% of hydrophobic carbon black (Denka Black: trade name of Denki Kagaku Kogyo Co., Ltd.) and 30% of polytetrafluoroethylene, and hydrophobic carbon black (Denka Black) ) 6
5% and 35% of polytetrafluoroethylene were mixed and dried, and the raw material powder of the diffusion layer was finely pulverized with a cohimill.
Sprinkle evenly at a rate of 0 g / m ² and place a plain weave
K carbon fiber fabrics were stacked. Further, a powder of the reaction layer was sprinkled on the carbon fiber fabric at a rate of 60 g / m ² through a sieve of 100 mesh similarly.

[0010] Then, using a hydraulic press, 30kg /
and cold forming at a surface pressure of cm ^2, 150mm × 150mm ×
A preformed sheet of 0.5 mmt was prepared. The reaction layer powder and the diffusion layer powder use a surfactant such as Triton X-100 (trade name) in order to enhance the dispersibility of carbon black and polytetrafluoroethylene in the raw material preparation process. A desurfactant removal treatment was performed at 3 ° C. × 3 hours. Thereafter, in order to impart water repellency to the electrode, sintering was performed by hot pressing at 380 ° C. × 10 kg / cm ² × 2 minutes to obtain a gas diffusion electrode.

Comparative Example 35% hydrophilic carbon black (Vulcan XC-72R), 35% hydrophobic carbon black (DENKA black), 30% polytetrafluoroethylene
Was mixed with the reaction layer raw material powder at a ratio of 1: 1.8, and a 0.2 mmt reaction layer sheet was obtained from a 3 mmt preformed sheet by a roll method. Hydrophobic carbon black (DENKA BLACK) 65
% And polytetrafluoroethylene 35% were mixed and dried, and solvent naphtha was mixed at a ratio of 1: 1.6 with a diffusion layer raw material powder.
mt of the diffusion layer sheet was obtained. A reaction layer sheet of 0.2 mmt and a diffusion layer sheet of 1 mmt are laminated, rolled further to 0.7 mmt by a roll, and after removing the surfactant at 280 ° C. × 30 minutes, at 380 ° C. × 175 kg / cm ² × 3 seconds. After sintering, a conventional diffusion electrode was obtained.

(Experimental Example) Chloroplatinic acid was applied by suction onto the gas diffusion electrode of the above embodiment and the above-mentioned conventional gas diffusion electrode.
Oxidation, reduction treatment in H ₂ atmosphere, 2mg / c
m ² of platinum was supported on the reaction layer to obtain a catalyst-carrying electrode. Then, a solid polymer electrolyte membrane (Nafion 117: trade name, manufactured by Du Pont) is sandwiched between the catalyst-carrying electrodes.
The cells were joined by hot pressing at 0 ° C. × 60 seconds to obtain cells.

Examples of the present invention For gas diffusion electrodes and gas diffusion electrodes manufactured by a conventional method, oxygen gas (helium carrier) was placed on one side of the electrode and pure helium gas was placed on the other side, with the electrodes separated. And the diffusion of oxygen gas into the pure helium gas stream was analyzed by gas chromatography to determine the gas diffusion coefficient. The reaction area is 180 cm ²
A power generation test was performed using a single cell, and an IV curve was obtained.
Table 1 shows the conditions of the power generation test and Table 2 shows the measurement results of the diffusion coefficient.

[0014]

[Table 1]

[0015]

[Table 2]

From the results shown in Table 2, it was found that the gas diffusivity of the gas diffusion electrode of the present invention was improved, and the performance of the electrode was significantly improved as shown in FIG.

[0017]

As described above, according to the present invention, it is possible to provide an electrode for a solid polymer electrolyte fuel cell in which the gas diffusivity of the electrode is improved and the cell performance is high.

[Brief description of the drawings]

FIG. 1 is a table showing a comparison between an IV curve of a gas diffusion electrode according to an embodiment of the present invention and a conventional gas diffusion electrode.

Claims (1)

(57) [Claims] 1. A reaction layer raw material powder comprising hydrophilic carbon black , hydrophobic carbon black and polytetrafluoroethylene and a diffusion layer raw material powder comprising hydrophobic carbon black and polytetrafluoroethylene are prepared in advance . On the support plate
The raw material powder for the reaction layer or the raw material powder for the diffusion layer is sprinkled through a sieve, and a porous carbonaceous substrate is placed thereon.
Sieve the above-mentioned diffusion layer raw material powder or reaction layer raw material powder
After sprinkling through, the whole is cold formed , then hot
A method for producing a gas diffusion electrode, comprising sintering by pressing .