JPS63116365A - Fuel cell - Google Patents

Abstract

PURPOSE:To produce a unit cell, the characteristic of which is not changed even if reaction gases are switched to each other for operation, by using electrodes symmetrical with respect to a matrix layer for both electrodes. CONSTITUTION:For the basic constitution of a unit cell, reaction gas passages 4a, 4b are formed on ribbed electrodes 3a, 3b, and catalyst layers 2a, 2b are formed on the opposite faces to the reaction gas passages 4a, 4b of the ribbed electrodes 3a, 3b respectively. When a fuel gas was fed through 4a of the unit cell and an oxidizer gas was fed through 4b for an electromotive test, a result shown by a solid line in the figure was obtained. Likewise, when the oxidizer gas was fed through 4a and the fuel gas was fed through 4b, a result shown by a dotted line in the figure was obtained. Accordingly, in the unit cell having the so called symmetrical air electrode and fuel electrode, the cell performance is not deteriorated even if the reaction gases are switched to each other for operation, thus indicating that the switching is feasible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a fuel cell, and particularly to the structure of a unit cell.

(Prior Art) As is well known, in a fuel cell, a matrix maintained as 8M quality is arranged between gas diffusion electrodes arranged oppositely.
Air or the like is used as an oxidant gas and gas containing hydrogen or the like is made to flow through the gas diffusion electrodes as a fuel gas.

For this reason, in a unit cell of a fuel cell, in order to maintain the best activity of the air electrode or fuel electrode, the configuration type, material type, composition heat treatment conditions, etc. of the electrode components (FFI electrode substrate, catalyst layer, etc.) must be adjusted. Each product is manufactured under the optimum conditions. Furthermore, although the air electrode and the fuel electrode have the same area, it is generally used that they have different shapes.

(Problem to be Solved by the Invention) However, in a unit cell in which the air electrode and the fuel electrode are not the same, it is difficult to operate the unit cell by exchanging the reaction gases flowing through the air electrode and the fuel electrode. This was one of the factors that degraded performance.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a fuel cell that can be operated with the reactive gases flowing through the air electrode and the fuel electrode being exchanged with each other.

[Structure of the invention]

(Means for Solving the Problems and Their Effects) In the present invention, by constructing a unit cell from electrodes that are symmetrical about the matrix layer, it becomes possible to exchange the flowing reaction gases with each other.

(Example) Hereinafter, an example of the present invention will be specifically described based on FIGS. 1 to 3.

FIG. 3 shows the basic configuration of the unit cell used in this example.

Reaction gas flow paths 4a and 4b are formed in the ribbed electrodes 3a and 3b. Catalyst layers 2a and 2b are formed on the surfaces of the ribbed electrodes opposite to the reaction gas flow passages 4a and 4b, respectively.

(Example 1) Carbon black powder supporting 4% by weight of platinum was 60% by weight.
The catalyst layer 2a was formed by heat-treating a catalyst layer containing 40% by weight of fluororesin at 330°C.

(Hereafter, the catalyst layer produced under these conditions will be referred to as catalyst layer I.) In addition, the catalyst layer consisting of 70% by weight of 3 cm black powder supporting 8% by weight of platinum and 30% by weight of fluororesin was heated at 350°C. The catalyst layer 2b was formed using the heat treated material. (Hereinafter, the catalyst layer produced under these conditions will be referred to as catalyst layer ①.) Further, 3a and 3b were porous carbon substrates having the same shape. The electrolyte layer was formed from ordinary silicon carbide (SiC) and fluororesin PTFE, and was later impregnated with phosphoric acid.

When an electromotive test was conducted by flowing fuel gas through 48 and oxidizing gas through 4b of the unit cell thus prepared, the cell exhibited the characteristics shown by the solid line in FIG. 2. Further, an electromotive test was conducted by passing oxidizing gas through 48 and fuel gas through 4b of a unit cell prepared in the same manner, and the results shown by the dotted line in FIG. 2 were obtained.

As shown in Fig. 2 of this example, in a unit cell in which the air electrode and the fuel electrode are so-called asymmetric, operating the reactor gases exchanged with each other leads to a deterioration in the cell performance. There is.

(Example 2) Using the unit cell shown in FIG. 3, the catalyst (2) shown in (Example 1) was formed on both 2a and 2b.

The porous substrates 3a and 3b and the electrolyte layer 1 were formed in the same manner as in Example 1.

When an electromotive test was carried out by flowing fuel gas through 48 and oxidizing gas through 4b of the unit cell thus prepared, the results shown by the solid line in FIG. 1 were obtained.

Further, oxidant gas was passed through 48 of a unit cell manufactured in the same manner, and fuel gas was passed through 4b. The results are shown by dotted lines in Figure 1.

As shown in Fig. 1 of this embodiment, in a unit cell in which the air electrode and the fuel electrode are symmetrical, even if the reactant gases are exchanged with each other during operation, the cell performance will not deteriorate; shows that it is possible.

However, in Example 1 and Example 2, the cells were operated under the following conditions.

(Normal pressure, 205℃, at220+nA/cd, U*
= UF = 40%) [Effects of the Invention] According to the present invention described above, by using electrodes that are symmetrical with respect to the matrix layer as the center, the characteristics can be improved even when the reactant gases are exchanged with each other during operation. It has become possible to produce a unit cell that does not change.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram of a unit cell related to the present invention, FIG. 2 is a characteristic diagram of a conventional cell, and FIG. 3 is a structural diagram of a unit cell. 1... Electrolyte layer. 2a, 2b...Catalyst layer, 3a, 3b...Porous electrode with ribs, 4a, 4b...Gas flow passage, Agent Patent attorney Noriyuki Chika Hirofumi Mitsumata No. 2 Renten Hitomi Shun No. 2 3 diagram

Claims (4)

[Claims] (1) In a fuel cell consisting of a positive electrode whose active material is an oxidizing gas such as air, a negative electrode whose active material is a fuel gas such as hydrogen, and an electrolyte layer sandwiched between the positive and negative electrodes, the positive and negative electrodes are of the same type. A fuel cell characterized in that it is formed from a catalyst. (2) The fuel cell according to claim 1, wherein the positive electrode and the negative electrode have the same shape. (3) The fuel cell according to claim 1, wherein the positive electrode and the negative electrode each have the same electrode structure. (4) The fuel cell according to claim 1, wherein the positive electrode and the negative electrode are each made of the same constituent members and the same composition.