JPS58150278A - Gas-separating plate for fuel cell - Google Patents

Abstract

PURPOSE:To prevent any stopping of reaction-gas supply grooves by forming films made of a hydrophilic matter, which has a higher wettability by water compared with carbon, on the surfaces of the reaction-gas supply grooves. CONSTITUTION:Films 3' and 4' made of a hydrophilic matter are formed on the surfaces of reaction-gas supply grooves 3 and 4 of a gas-separating carbon plate 2. The above hydrophilic matter not only should have a higher wettability by water compared with carbon, but also should have acid resistance and heat resistance. For instance, aluminum oxide, silicon dioxide or titanium oxide can be used as the above hydrophilic matter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carbon gas separation plate for a matrix fuel cell using an acidic electrolyte such as phosphoric acid. It facilitates supply.

The gas separation plate (2) interposed between the unit cells (1) is generally obtained by hot pressing a mixed powder of graphite and a binder (phenolic resin) and then carbonizing the binder by high temperature heat treatment. On both the front and back sides,
Each supply groove (3
1+41, and serves as a separator for both gases and a connecting conductor between the unit cells.

Each reaction gas passes through these supply grooves +31+41e and diffuses into the air electrode (5) and hydrogen electrode f61K, respectively, and this diffused gas causes an electrochemical reaction via the electrolyte matrix (7).

However, the surface of the separation plate has a considerable water supply property, and the cross section of each supply groove +3+ +41 has a width of 1.5 to 2. Off
Since the height is extremely small at about 11'll, the water generated by the battery reaction, especially this generated water, is absorbed by the high concentration phosphoric acid electrolyte eluted from the gas into the supply groove f31 +41 of the separation plate (2). Attach to. The former generated water is evaporated and removed in a short time depending on the battery operating temperature, but water containing phosphoric acid is difficult to evaporate, so it forms droplets and blocks the supply groove +3+ 141, causing a reaction to this groove. Gas supply was not carried out smoothly, resulting in uneven electrode reactions and contributing to battery deterioration.

The present invention eliminates the clogging of the reaction gas supply groove, and is characterized by the fact that on the surface of the reaction gas supply groove,
By forming a film of a hydrophilic material (lower contact angle with water) that is more easily wetted by water than carbon, water containing electrolyte adhering to the grooves of the separation plate is diffused onto the groove surface and becomes droplets. The purpose of this method is to prevent this, and to evaporate and remove the liquid that has spread onto the coating, thereby facilitating the supply of the reaction gas.

The hydrophilic substance mentioned above must not only be more easily wetted by water than carbon, but also have acid resistance and heat resistance, such as aluminum oxide (Aj?zOa),
Examples include silicon dioxide (Si02) and titanium oxide (TiO2).

There are two methods for forming the film: one is to deposit an oxide directly on the surface of the groove, and the other is to deposit metal on the surface of the groove and then oxidize it. There are two methods: chemical vapor deposition (Va, por plating) and chemical vapor deposition (Va, por plating).

Firearm spraying is a method in which powder or rod-shaped coating materials are baked onto the groove surface with oxygen acetylene red, etc., and chemical vapor deposition is also called a gas phase reaction method, which uses gas reaction and hydrogen reduction of volatile compounds at high temperatures. This method deposits a thin film on the groove surface.

As an embodiment of the present invention, the case where aluminum oxide is coated on the grooves +31 to +41 of the gas separation plate (2) by chemical vapor deposition is explained. , Ae2XO3 film +3+'t41' by the reaction of the following formula % formula %
form.

The thickness of the coating was approximately 10 μm.

The electrode (5+ +
Either mechanically scrape off the coating that adheres to the contact surface with 61, or
Masking may be performed in advance with tape or the like to prevent a film from adhering to the contact surface with the electrode.

As mentioned above, in the carbon gas separation plate according to the present invention, the reaction gas supply grooves are covered with a thin film of a hydrophilic substance, so that the supply grooves absorb the electrolyte due to the hydrophilicity on the surface of the separation plate. No more clogging caused by the contained droplets,
The liquid adhering to the supply groove diffuses through the hydrophilic coating and is evaporated and removed without forming droplets.

Therefore, the reaction gas is sent smoothly and evenly to each supply groove, thereby improving battery characteristics and life.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a battery stack equipped with a gas separation plate of the present invention, and FIG. 2 is an enlarged sectional view of the same essential parts. 1... Unit cell, 2... Gas separation plate, 5.4...
Reaction gas supply groove, 6', 4'... coating, 5.6...
Electrode, 7... electrolyte matrix. Applicant Sanyo Electric Co., Ltd. Agent Patent Attorney Shizuo Sano 1 3 675

Claims (3)

[Claims] (1) A gas separation plate for a fuel cell, characterized in that a film made of a hydrophilic substance is formed on the surface of the reaction gas supply groove of the carbon gas separation plate. (2) A gas separation plate for a fuel cell according to claim 1, wherein the hydrophilic substance is selected from the group consisting of aluminum oxide, silicon oxide, and titanium oxide. (3) A gas separation plate for a fuel cell according to claim 1, wherein the coating has a thickness of about 10 μm.