JPS6322421B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in gas separation plates for fuel cells.

The carbon separator of a matrix fuel cell using an acidic electrolyte has the function of supplying each reactive gas to the back of each negative and positive gas electrode (hydrogen electrode and air electrode), and the function of supplying the respective reaction gases to the back of the negative and positive gas electrodes (hydrogen electrode and air electrode). It functions as a connecting conductor between unit cells made up of a matrix. Furthermore, for the former function, it is necessary to be non-porous in order to completely separate hydrogen and air.

Such gas separation plates are made by mixing graphite powder with binder powder such as phenolic resin, hot pressing, and then heat-treating at high temperature (approximately 1000℃) for a long time to carbonize the binder. be done.

As shown in the plan view of FIG. 1 and the cross-sectional views of FIG. Although a large number of hydrogen gas supply ports (a) and air supply grooves (c) are formed, the mold is complicated to create and the separation plate is difficult to manufacture. For example, if the area of the separation plate becomes large, uneven filling of the powder material will occur, resulting in uneven thickness, and the separation plate will become deformed or warped due to the large number of grooves (R) and (C), resulting in poor yield. There was a problem.

The gas separation plate according to the present invention is composed of a flat non-porous carbon substrate and porous strips made of carbon paper as a base material and arranged at a predetermined interval on the substrate, and as described above. This eliminates the causes of defective products and improves the diffusion of the supplied reaction gas to the electrode surface.

An example of this will be explained below with reference to FIG.
For the gas separation plate 1 of the present invention, first, a flat carbon nonporous substrate 2 without gas supply grooves is prepared by the above-mentioned conventional method.

Next, several sheets (3 to 4 sheets) of water-repellent porous carbon paper (thickness: approximately 0.5 mm) are stacked on both sides of this substrate 2, but each stacked surface is not entirely covered but only partially. It is integrated by pasting it on with a fluororesin adhesive. This carbon stack 3 (thickness 1.5~2
mm) are cut and removed with a slitter at intervals of 2 to 2.5 mm to form a large number of porous strips 4, 3 to 5 mm wide.
5, gas passages 6, 7 are formed between these strips.

The strength of the substrate 2 can be supplemented by leaving one or two sheets of carbon paper 8, 9 as shown in the figure when the carbon paper stack 3 is cut. Of course, in this case, the number of stacked bodies 3 may be increased accordingly.

Finally, a coating layer of a fluororesin adhesive such as Eight Seal (trade name) is formed as a gas sealing material on the longitudinal end faces A and B of the porous strips 4 and 5 located on both sides to complete the process.

The above example describes the case of stacking thin carbon papers, but if thick carbon paper with a thickness of 1.5 to 2 mm is used, a gas separation plate can be created in the same manner as above without stacking. can do.

Furthermore, the water-repellent treatment of the carbon paper used in the present invention is carried out by immersing it in a fluororesin dispersion, pulling it up, and then heat-treating it at the binding temperature of the resin, similar to the carbon paper lining the catalyst layer (waterproof layer) in the gas electrode. However, the content of fluororesin in the carbon paper is about 40% in the case of the electrode waterproof layer, whereas it is about 5% in the case of the present invention, which does not impair the conductivity and porosity of the carbon paper.

As mentioned above, the gas separation plate of the present invention is composed of a flat non-porous carbon substrate and porous strips arranged at predetermined intervals (gas passages) on this substrate. Unlike conventional separation plates, a complicated mold is not required, and the separation plate does not suffer from deformation or warpage caused by grooves, thereby improving the yield. In addition, the reaction gas that passes through the gas passages between the porous strips made of carbon paper as a base material can diffuse, so not only the electrode surface facing the gas passages but also the electrode surface in contact with the strips can be diffused. The reactant gas is also supplied to the plate, and the plate can fully perform its gas supply function as a gas separation plate without impairing the electrode reaction.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a conventional gas separation plate, FIGS. 2a and 2b are sectional views taken in directions perpendicular to each other in FIG. 1, and FIG. 3 is an oblique view of a gas separation plate according to the present invention. . 1... Gas separation plate, 2... Non-porous carbon substrate, 3
... Carbon paper stack, 4, 5... Porous strip, 6, 7... Passage, 8, 9... Carbon paper,
A, B...Gas seal surface (coating layer).

Claims (1)

[Claims] 1. Porous strips made of carbon paper are arranged at predetermined intervals on the surface of a flat non-porous carbon substrate, and gas passages are formed between the strips. A gas separation plate for a fuel cell characterized by: 2. The gas separation plate for a fuel cell according to claim 1, wherein the porous strip is constructed by stacking a plurality of sheets of carbon paper. 3. The gas separation plate for a fuel cell according to claim 2, wherein a thin carbon paper supporting the porous strip is attached to the entire surface of the substrate.