JPH0652873A - Fuel cell - Google Patents

Abstract

PURPOSE:To maintain the stable performance of a fuel cell over a long period of time by ensuring that an electrode member constituting a pair of porous electrodes disposed with a layer of electrolyte sandwiched therebetween is prevented from corroding. CONSTITUTION:An electrode member 17 is provided which constitutes a pair of porous electrodes 3a, 3b disposed in such a way that a layer 1 of electrolyte is sandwiched therebetween. Notched recessed portions 25 are provided at the four corners of the electrode member 17 and blocks 24 of carbon are fitted into the notched portions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell in which an electrode member constituting a pair of porous electrodes forming a catalyst layer holds an electrolyte, and more particularly to a catalyst non-coated portion at an edge portion of the electrode member. And a fuel cell having a wet seal portion.

[0002]

2. Description of the Related Art Conventionally, a fuel cell has been known as a device for directly converting chemical energy of fuel into electric energy. This fuel cell can convert the energy released along with the oxidation reaction into electric energy by oxidizing the fuel by a gas chemical process. The thermal efficiency of power generation of such a fuel cell reaches 40 to 50% even on a relatively small scale. Therefore, it is expected that the thermal efficiency will far exceed that of the new thermal power generation, and it is of great interest.

Here, the structure and operating principle of the fuel cell will be briefly described. A fuel cell is formed by stacking a plurality of unit cells each having a pair of porous electrodes forming a catalyst layer and an electrolyte layer disposed between the porous electrodes with a separator interposed therebetween. Among them, the porous electrode forming the catalyst layer is composed of an anode electrode (fuel electrode) and a cathode electrode (oxidizer electrode), and stores an electrolyte in the form of an aqueous solution in a porous body (substrate). The electrolyte layer is formed by impregnating an electrolyte aqueous solution into a porous layer containing electrolyte-resistant fine particles as a main raw material.

In the fuel cell having such a structure, a fuel gas such as hydrogen is brought into contact with the back surface of the anode electrode, and an oxidant gas such as oxygen is brought into contact with the back surface of the cathode electrode. Electrical energy can be extracted from the pair of electrodes using a chemical reaction. Moreover, the fuel cell can extract electric energy with high conversion efficiency as long as the fuel gas and the oxidant gas are supplied.

Here, a conventional example of a fuel cell based on the above principle will be specifically described with reference to FIGS. 3 and 4. First, FIG. 3 is a vertical cross-sectional perspective view of a configuration example of a unit cell in a ribbed electrode type fuel cell using phosphoric acid as an electrolyte. In the figure, 1 is an electrolyte layer, which is impregnated with a phosphoric acid aqueous solution. Reference numerals 3a and 3b are an anode electrode and a cathode electrode made of a porous carbon material, which are arranged with the electrolyte layer 1 interposed therebetween. Catalysts 2a and 2b are applied to the sides of the electrodes 3a and 3b that are in contact with the electrolyte layer 1, respectively.

Also, ribs 4a and 4b and a groove 5 through which fuel gas and oxidant gas flow are provided on the back side of each electrode 3a and 3b.
a and 5b respectively. The groove 5a through which the fuel gas flows and the groove 5b through which the oxidant gas flows extend in directions orthogonal to each other and are regularly arranged in parallel. A unit cell is formed as described above, and a plurality of such unit cells are laminated with the dense carbonaceous separator 6 sandwiched therebetween to form a unit cell laminated body.

Next, the structure of the fuel cell including the unit cell stack will be described with reference to FIG. The unit cell laminated body has a current collector plate 7, an insulating plate 8, a clamping plate 9 and a terminal 10 attached to the upper and lower ends thereof, and is clamped from above and below with an appropriate clamping pressure. Further, a pair of manifolds 12 and 13, 14 and 15 for supplying and discharging the fuel gas and the oxidant gas through the pipe 16 through the gasket 11 are opposed to the side surfaces of the unit cell laminated body, respectively. By arranging and tightening and fixing with appropriate pressure,
It constitutes a fuel cell.

By the way, the anode electrodes 3a and the cathode electrodes 3b are coated with the catalysts 2a and 2b on the side in contact with the electrolyte layer 1. However, since the catalysts 2a and 2b are expensive, it is possible to save the usage amount. desirable. For example, as shown in FIG. 5, in the electrode member 17 forming the anode electrode 3a and the cathode electrode 3b, only the portion where the gas flow grooves 5a and 5b intersect each other, that is, the substantially square portion at the center of the electrode member 17 is the catalyst 2a. , 2b are applied to form a catalyst coating section 18. That is, in the electrode member 17, there is the catalyst non-coating portion 19 around the portion where the gas flow grooves 5a and 5b do not intersect with each other, that is, around the catalyst coating portion 18, and thereby the amount of catalyst used is saved. ing.

Since the catalyst is not coated on the catalyst non-coating portion 19, no current flows during operation of the fuel cell and the potential is high. As a result, the electrode member 17 may be corroded at a position corresponding to the catalyst non-coating portion 19. In particular, this phenomenon is more remarkable on the cathode electrode 3b side, and further, in the cathode electrode 3b, the portion having the oxidant gas flow groove 5b on the back surface becomes an oxidizing atmosphere, and therefore corresponds to those in the electrode member 17. The parts are very susceptible to corrosion.

Therefore, in order to prevent this corrosion, FIG.
As shown in FIG.
It has been considered to provide the water treatment section 20 having a width larger than the width of the catalyst non-application section 19 at the edge portions on the inlet side and the outlet side of b. The water solution of the water treatment section 20 can repel the phosphoric acid aqueous solution. Therefore, the electrolyte does not come into contact with the electrode portion 17, and the corrosion of the electrode portion 17 can be prevented.

[0011]

However, the above-mentioned conventional fuel cells have the following problems to be solved. That is, in order to prevent the loss of phosphoric acid, which is the electrolyte, in the cathode electrode 3b, the cathode electrode 3b has a structure as shown in
A wet seal portion 22 is attached to the edge portion as shown in FIG. Since the wet seal portion 22 is configured to always contain water, the drainage treatment portion 20 cannot be provided in this portion. Therefore, although the corner portion of the cathode electrode 3b is exposed to the high electric potential and easily corroded as described above, the water treatment for preventing this cannot be performed. As a result, the electrode member 17 at this position
It was very easy for the fuel cell to corrode, and it was difficult for the fuel cell to maintain stable performance over a long period of time.

The fuel cell of the present invention has been proposed in order to solve the above problems, and its purpose is to ensure the corrosion of the electrode members constituting the pair of porous electrodes arranged so as to sandwich the electrolyte layer. (EN) Provided is a fuel cell which prevents and maintains stable performance for a long period of time.

[0013]

SUMMARY OF THE INVENTION The present invention comprises a fuel cell having an electrode member composed of a pair of porous electrodes forming a catalyst layer so as to sandwich an electrolyte layer impregnated with an electrolyte, the electrode member holding an electrolyte. In, the electrode member,
A structural feature is that a catalyst non-coating portion and a wet seal portion are provided at the edge portion and cutout portions are provided at four corner portions.

[0014]

In the fuel cell of the present invention, since the notches are provided at the four corners of the electrode members constituting the pair of porous electrodes, the wet seal portion and the catalyst non-coating portion are present at the edge portions of the electrode members. However, this position is not exposed to high potential. Therefore, it is possible to prevent corrosion of the electrode member at the edge portion of the electrode member.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to FIG. It should be noted that the same parts as those of the conventional example shown in FIG. As shown in FIG. 1, recesses 25 are provided as cutouts at the four corners of the electrode member 17. The concave portion 25 is a square whose one side is shorter than the width of the edge seal portion 22. In addition, after the electrode plates are stacked in the recess 25, the carbon block 24 having the same size and a high degree of graphitization and which is impermeable to gas is formed.
Inset. The electrode member 17 is the anode electrode 3a.
The gas flowing through the gas flow groove 23 in the drawing can be appropriately selected depending on the type of electrode.

In the fuel cell of this embodiment having such a structure, since the recesses 25 are provided at the four corners of the electrode member 17, the wet seal portion 22 and the catalyst non-coating portion are provided at the edge portion of the electrode member 17. Even if it exists, since the electrode member 17 itself does not exist at the four corners of the electrode member 17, this position is not exposed to a high potential, and the corrosion of the electrode member 17 can be prevented. According to the present embodiment as described above, since the corrosion of the electrode member 17 can be reliably prevented, the fuel cell can exhibit stable performance for a long period of time.

The fuel cell of the present invention is not limited to the above embodiment, and the shape of the notch can be changed as appropriate. For example, as shown in FIG.
At one corner, the length of the short side is the edge seal part 2.
It also includes an embodiment in which a rectangular recess 26 shorter than the width of 2 is provided. A carbon block 27 having the same shape as the recess 26 is fitted into the recess 26. This carbon block 27
Is made of the same material as the carbon block 24. Even in such an embodiment, the same effects as those of the above embodiment can be expected.

[0018]

As described above, according to the present invention, the electrode member 4 composed of a pair of porous electrodes forming a catalyst layer is provided.
It is possible to prevent corrosion of the electrode member by the simple structure of providing notches at the two corners,
This makes it possible to provide a fuel cell having stable performance over a long period of time.

[Brief description of drawings]

FIG. 1 is a plan perspective view of an electrode plate showing a first embodiment of the present invention.

FIG. 2 is a plan perspective view of an electrode plate showing a second embodiment of the present invention.

FIG. 3 is a sectional perspective view showing a unit cell of a fuel cell.

FIG. 4 is an exploded perspective view showing a fuel cell.

FIG. 5 is a transparent plan view of a cathode electrode plate in a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolyte layer 3a Anode electrode 3b Cathode electrode 5a Fuel gas distribution groove 5b Oxidizing gas distribution groove 17 Electrode plate 18 Catalyst coating part 19 Catalyst non-coating part 20 Water treatment part 21 Oxidizing gas distribution groove 22 Edge seal part 23 Gas distribution Groove 24 Carbon block 25 Recess 26 Rectangular recess

Claims (1)

[Claims] 1. A fuel cell comprising an electrode member comprising a pair of porous electrodes forming a catalyst layer so as to sandwich an electrolyte layer impregnated with an electrolyte, the electrode member holding an electrolyte, wherein the electrode member is an edge. A fuel cell having a catalyst non-coated portion and a wet seal portion in a portion and cutout portions provided in four corner portions.