JP3058220B2 - Manufacturing method of gas diffusion electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell, a secondary battery,
The present invention relates to an improvement in a method of manufacturing a gas diffusion electrode used for an electrochemical reactor, a plating anode, and the like.

[0002]

2. Description of the Related Art Conventionally, as a method for manufacturing a gas diffusion electrode,
There is a method in which a platinum catalyst is attached to carbon powder, mixed with a polytetrafluoroethylene powder, pressed, and then sintered to form a reaction layer.

[0003]

By the way, the gas diffusion electrode composed of the reaction layer produced by the above-mentioned production method is prepared by firing carbon powder and polytetrafluoroethylene to which a platinum catalyst is attached, as pressed. Since the powder is relaxed due to the thermal expansion of the powder at a high temperature without being tied, the passage of the electrolyte and the gas is often disconnected. Therefore, some platinum catalysts in the reaction layer do not come into contact with the electrolytic solution and do not contribute to the reaction, and the contact area between the electrolytic solution and the gas is not sufficient and the catalytic performance is low.

[0004] In view of the above, recently, as a method of manufacturing a gas diffusion electrode which can ensure an electrolyte infiltration passage and a gas diffusion passage without interruption, a hydrophilic carbon powder and a water-repellent carbon powder are used. And a water-repellent binder, followed by hot pressing, and then immediately quenching or cooling in a pressed state to form a reaction layer.

However, in this method of manufacturing a gas diffusion electrode, since hot pressing is performed, it is not possible to press-mold the entire surface to a uniform thickness and hold and fix the carbon powder by bonding the water-repellent binders together. In addition, the plane area is limited, and a large gas diffusion electrode cannot be manufactured.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing a gas diffusion electrode which can be manufactured without a hot press, and which can be easily increased in size, is inexpensive and has high catalytic performance.

[0007]

Means for Solving the Problems To solve the above-mentioned problems, a method for producing a gas diffusion electrode according to the present invention comprises the steps of:
Water-repellent carbon powder, Ri Do and a water-repellent binder, pre solvent extraction
A reaction layer material sheet removing the surfactant by law, water-repellent carbon powder, Ri Do and a water-repellent binder, in advance solvent extraction
The composite sheet with the gas diffusion layer material from which the surfactant has been removed is subjected to cold pressing and then heat treatment.

[0008]

As described above, according to the gas diffusion electrode manufacturing method of the present invention, the reaction layer material sheet from which the surfactant has been removed in advance and the gas diffusion layer material sheet are cold-pressed and then heat-treated. Without this, the carbon powder in the reaction layer and the gas diffusion layer is held and fixed by the combination of the water-repellent binders and does not relax, so that the infiltration passage for the electrolytic solution and the gas diffusion passage are secured without interruption. Since a hot press is not required, a large gas diffusion electrode can be easily and inexpensively manufactured.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for producing a gas diffusion electrode according to the present invention will be described. A hydrophilic and water-repellent carbon powder (6: 4) having an average particle diameter of 420 °, triton and water are mixed and stirred in a colloid mill. Then, a mixture obtained by mixing and diffusing a polytetrafluoroethylene dispersion having an average particle size of 0.3 μm was mixed and kneaded with carbon powder and polytetrafluoroethylene powder in a ratio of 7: 3. The mixture is poured into a filter and filtered to form a cake on a filter plate. On the other hand, a water-repellent carbon powder having an average particle size of 420 °, water and Triton were mixed and stirred by a colloid mill , and a polytetrafluoroethylene dispersion having an average particle size of 0.3 μm was added thereto, followed by mixing and stirring. The polytetrafluoroethylene powder is put in a ratio of 6.5: 3.5 and kneaded, and this mixed solution is poured into a filter and filtered to form a cake on a filter plate. Next, roll each cake by rolling it 200mm wide, 500mm long and 0.2mm thick, 1.0mm
After producing the sheet over preparative reaction layer material and the gas diffusion layer material of mm, and dried at 80 ° C. to evaporate the water and solvent naphtha,
The surfactant (Triton) was extracted with ethanol using a Soxhlet extractor for 12 hours. Next, the sheet in which the material was composited was cold-pressed at a pressure of 200 kg / cm ² and heat-treated at 320 ° C. for 30 minutes to convert the carbon powder in the material composite sheet into polytetrafluoroethylene powder. A large gas diffusion electrode was made by holding and fixing each other by joining each other.

[0010] The gas diffusion electrode thus produced by the production method of the present invention is provided without interruption of the electrolyte infiltration passage and gas diffusion passage in the reaction layer, and the gas diffusion passage is secured in the gas diffusion layer without interruption. Was done.

When the gas diffusion electrode of this embodiment is used in, for example, a fuel cell, the electrolyte penetrates into all the electrolyte inflow passages formed by the hydrophilic carbon powder in the reaction layer, and the gas flows into the gas diffusion layer and the reaction layer. The gas diffuses and penetrates all the gas diffusion passages formed by the water-repellent carbon powder and the water-repellent polytetrafluoroethylene powder in the layer, and the contact between the electrolyte and the gas is sufficient, and the reaction is promoted.

In order to further improve the catalytic performance, a catalytic metal such as a platinum group metal, gold, silver, nickel, cobalt or the like, or an oxide thereof, or both is attached to the hydrophilic carbon powder in the reaction layer. It is a good thing.

[0013]

As described above, according to the method for producing a gas diffusion electrode of the present invention, a reaction layer material sheet from which a surfactant has been removed in advance and a gas diffusion layer material sheet are cold-pressed and then heat-treated. Without pressing, the carbon powder in both material sheets is held and fixed by the combination of the water-repellent binders, and the electrolyte inflow passage and gas diffusion passage are secured without interruption, and the contact area between the electrolyte and the gas is reduced. An excellent gas diffusion electrode which is sufficient and has extremely high catalytic performance can be obtained. Since a hot press is not required, a large gas diffusion electrode can be easily and inexpensively manufactured.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/86-4/98

Claims (1)

(57) [Claims] 1. A hydrophilic carbon powder, water repellent carbon powder, Ri Do and a water-repellent binding agent, take a surfactant in advance solvent extraction removal
A reaction layer material sheet had water repellency carbon powder, Ri Do and a water-repellent binder, a composite sheet with <br/> gas diffusion layer material removing the surfactant was cold pressed at a pre solvent extraction method Thereafter, a heat treatment is performed.