JPH06310160A - Fuel cell - Google Patents

Abstract

PURPOSE:To obtain a fuel cell with an excellent durability and safety by preventing a electrolytic corrosion of the reaction gas feeding parts and the exhaust parts of the oxidizer gas flowing grooves of a cathode. CONSTITUTION:An anode 8 and a cathode 9 to be a pair of electrodes are provided by placing a matrix layer 10 impregnating an electrolyte at the center. On the back surfaces of the electrodes, reaction gas flowing grooves 11 and 12 are formed. The cathode 9 is formed by providing a water repelling treatment to the gas feeding parts and the gas exhaust parts 12a of the reaction gas flowing grooves 12 and near the parts 12a by the PTFE and the like beforehand. As a result, the impregnation and the infiltration of the electrolyte to the water repelling treatment parts 13 are not generated, and an electrolytic corrosion can be prevented. Consequently, a fuel cell with an excellent durability and safety can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell, and more particularly to a technique for improving the durability of a fuel cell by preventing electrolytic corrosion of a cathode electrode in a power generation stack.

[0002]

2. Description of the Related Art A fuel cell is a device that directly oxidizes a fuel having chemical energy by an electrochemical process to directly convert the energy released by the oxidation reaction into electrical energy. This fuel cell power generation system has a thermal efficiency of 40-50% for power generation even on a relatively small scale.
It is expected to be a high-efficiency power generation system that far surpasses new thermal power generation systems because it has the feature of reaching the maximum. Further, there are features such as very little emission of SOx and NOx, which are pollution factors which have become a big social problem in recent years, a large amount of cooling water is not required because a power generation device does not include a combustion cycle, and vibration is small. From that,
There is also an advantage that there are few environmental problems such as noise and exhaust gas.
Furthermore, it has excellent characteristics such as good responsiveness to load fluctuation, theoretically high conversion efficiency, and suitable for cogeneration system that uses heat at the same time as power generation. Expectations and interest have been attracted, and practical application is imminent.

Such a fuel cell will be specifically described with reference to the drawings. FIG. 3 is a perspective view showing a structure of a fuel cell body of a general fuel cell, and FIG. 4 is a perspective view schematically showing a unit cell which is also a constituent member of the fuel cell body. As shown in FIG. 3, a laminated body 1 formed by laminating a plurality of unit cells for power generation and cooling plates for discharging heat generated in the unit cells, and a tightening plate for fastening the laminated body 1 from both upper and lower sides. 2, a spacer 3 inserted between the laminated body 1 and the tightening plate 2, a gas manifold 4 for supplying and discharging a reaction gas 4,
5 includes an anode manifold 4, a cathode manifold 5, and a sealing material 6 that seals between the gas manifolds 4, 5 and the laminated body 1.

In the unit cell 7, as shown in FIG. 4, a pair of electrodes, an anode electrode 8 and a cathode electrode 9, are arranged with a matrix layer 10 impregnated with an electrolyte interposed therebetween. For both the anode electrode 8 and the cathode electrode 9, a carbonaceous porous substrate, for example, a substrate made of carbon paper made of thin carbon fiber is used, and the surface of the substrate in contact with the matrix layer 10 is The catalyst layers 8a and 9a are formed. Such an anode electrode 8 and a cathode electrode 9 are both gas diffusion electrodes with ribs (gas diffusion electrodes with reaction gas flow grooves)
As a result, a large number of reaction gas flow grooves 11 and 12 are formed on the surface opposite to the matrix layer 10 (hereinafter referred to as the back surface).
The pair of facing edge portions 8x, 8x; 9x, 9x are formed in parallel so as to be connected to each other. A fuel gas such as hydrogen is supplied to the reaction gas flow groove 11 of the anode electrode 8 and an oxidant gas such as oxygen is supplied to the reaction gas flow groove 12 of the cathode electrode 9 to flow therethrough. The groove 11 and the oxidant gas flow groove 12 are arranged so as to be orthogonal to each other.

The fuel cell utilizes an electrochemical reaction caused by such a structure to output electric energy between the electrodes. In this case, the output voltage of the unit cell composed of a pair of anode electrode and cathode electrode is
Since it is very low at 0.7-0.8V under normal operating conditions,
In a practical machine, a predetermined output voltage is obtained by stacking unit cells in series to form a fuel cell body.

[0006]

By the way, in the conventional fuel cell as described above, at the time of its operation, a part of the electrolyte is vaporized and mixed into the reaction gas, and the reaction gas flows in the reaction gas flow groove together with the reaction gas. The phenomenon of flowing and being taken out of the battery occurs, and the amount of electrolyte in the matrix layer decreases with the lapse of operating time. Such electrolyte loss greatly affects the life of the fuel cell. For this reason,
As a means of compensating for the loss of the electrolyte, an electrolyte storage layer is provided,
A method has been proposed in which the substrate of each of the electrodes 8 and 9 and the catalyst layer are supplied to the matrix layer 10 as an electrolyte supply route.

However, since the electrolyte is an acidic solution such as phosphoric acid, it is highly corrosive (electrolytic). When the influence of such a highly corrosive electrolyte impregnating and permeating into each electrode was examined, the effect on the electrode was examined. The electrode 9 portion, that is, the reaction gas supply portion and the discharge portion 12 between the seal materials 6 and 6 at both ends of the oxidant gas flow groove 12 and the edge portion 9y thereof.
In a, it was found that the substrate of the cathode electrode 9 was softened by electrolytic corrosion.

When such a fuel cell is operated for a long time, the strength of the cathode electrode 9 is extremely lowered, and in some cases, the reaction gas flow groove 12 is locally crushed to hinder the flow of the reaction gas. Also becomes. Therefore, it may be impossible to continue the operation of the fuel cell due to the destruction of the reaction gas flow groove 12 of the cathode electrode 9 or the occurrence of crossover between the oxidant gas and the fuel gas.

The present invention has been made to solve the above-mentioned problems in the prior art, and an object thereof is to prevent electrolytic corrosion in the reaction gas supply portion and the discharge portion of the oxidant gas flow groove of the cathode electrode. This is to provide a fuel cell having excellent durability and safety.

[0010]

In order to achieve the above object, in the present invention, an anode electrode to which a fuel gas is supplied and a cathode electrode to which an oxidant gas is supplied are arranged with an electrolyte layer interposed therebetween. A fuel cell in which cells are formed and a plurality of the unit cells are laminated is characterized in that the reaction gas supply portion and the discharge portion of the cathode electrode are subjected to water repellent treatment.

[0011]

In the fuel cell of the present invention, since the reaction gas supply part and the discharge part of the electrode (cathode electrode) to which the oxidant gas is supplied are subjected to the water repellent treatment, that part is operated by the fuel cell. It is possible to prevent electrolytic corrosion. As a result, even when the fuel cell is operated for a long time, the electrode is not broken and the durability and safety are improved.

[0012]

An embodiment of the fuel cell according to the present invention will be described below with reference to the drawings. Here, FIG. 1 schematically shows the cathode electrode of the fuel cell, (a) is a rear view, and (b) is
FIG. 3 is a side view of the gas distribution groove on the side of a supply unit or a discharge unit.
2 is a perspective view schematically showing a unit cell including the cathode electrode of FIG. The members having the same functions as those of the conventional gas circuit breaker are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 1, in this embodiment, the reaction gas flow groove 12 provided on the back surface of the cathode electrode 9 has
Water repellent treatment (water repellent treatment portion 13-hatched portion) is performed on the gas supply portion and the discharge portion 12a and their vicinity. Such a cathode electrode 9 has both end portions of the reaction gas flow groove 12 of the gas diffusion electrode with ribs and its edge portion 9y.
Reaction gas supply section and discharge section 1 between the sealing materials 6 and 6
2a is impregnated with PTFE dispersion (for example, Mitsui Fluorochemical, solid content 60%) and dried,
It is formed by forming the catalyst layer 9a and performing heat treatment at 360 ° C. As a result, the water-repellent portion 13 is provided in the gas supply portion and the discharge portion 12a of the reaction gas flow groove 12 and in the vicinity thereof.
The cathode electrode 9 is formed in a state in which is previously provided. After that, at the time of forming the unit cell, the electrolyte is impregnated and permeated into the cathode electrode 9 which has been subjected to the water repellent treatment. Using the cathode electrode 9 thus formed,
A unit cell 7 as shown in FIG. 2 is formed.

A unit fuel cell having the above-mentioned structure and the conventional unit cell shown in FIG. 3 are laminated by 25 sheets to prepare a test fuel cell. Each test fuel cell was subjected to a continuous test for 5000 hours under normal fuel cell operating conditions. As a result, in the prior art, the reaction gas flow groove of the cathode electrode was softened by electrolytic corrosion. Further, locally, the groove was crushed to a state where the flow of the reaction gas was obstructed. On the other hand, in this example, the softening and crushing of the reaction gas flow groove were not observed.

As described above, in the fuel cell of this embodiment, since the cathode electrode 8 is formed by the water repellent treatment at the gas supply portion and the discharge portion 12a which are both ends of the reaction gas flow groove 12, Impregnation of the water repellent treated part 13 with electrolyte solution
It will not penetrate, and electrolytic corrosion can be prevented. As a result, in the fuel cell of the present embodiment, even if the fuel cell is operated for a long time, the oxidant gas flow groove 1 of the cathode electrode 9
No destruction of No. 1 or generation of crossover between the oxidant gas and the fuel gas does not occur, and high durability and safety can be obtained.

The present invention is not limited to the above-mentioned embodiments, but the specific constitution can be appropriately changed except for the cathode electrode. In addition, the present invention is not limited to the electrode in which the reaction gas flow groove used in the example is formed in advance, and also in the case where the reaction gas flow passage is provided in a flat electrode, both end portions of the reaction gas flow passage are similarly formed. Also, the same effect as in the above-described embodiment can be obtained by forming the cathode electrode by subjecting the gas supply portion and the discharge portion, which are the electrode edge portions connected thereto, to the water repellent treatment to form the cathode electrode.

[0017]

As described above, according to the present invention, since the reaction gas supply portion and the discharge portion of the cathode electrode are subjected to the water repellent treatment, impregnation and permeation of the electrolyte into this portion do not occur, and electrolytic corrosion is prevented. Can be prevented. As a result, a fuel cell having excellent durability and safety can be provided.

[Brief description of drawings]

FIG. 1 schematically shows a cathode electrode of an embodiment of a fuel cell of the present invention, (a) is a rear view, and (b) is a side view of a gas distribution groove on the side of a supply part or a discharge part.

FIG. 2 is a perspective view schematically showing a unit cell including the cathode electrode of FIG.

FIG. 3 is a perspective view showing a structure of a fuel cell body of a conventional fuel cell.

FIG. 4 is a perspective view schematically showing a unit cell which is a constituent member of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laminated body 2 ... Clamping plate 3 ... Spacer 4 ... Anode manifold 5 ... Cathode manifold 6 ... Sealing material 7 ... Unit cell 8 ... Anode electrode 8a ... Catalyst layer 9 ... Cathode electrode 9a ... Catalyst layer 10 ... Matrix layer 11 ... Reaction gas flow groove 12 of anode electrode ... Reaction gas flow groove 12a of cathode electrode ... Gas supply part and discharge part 13 ... Water repellent treatment part

Claims (1)

[Claims] 1. An anode electrode to which a fuel gas is supplied,
In a fuel cell in which a unit cell is formed by arranging cathode electrodes to which an oxidant gas is supplied with an electrolyte layer in between, and a plurality of unit cells are stacked, water repellency is applied to the reaction gas supply unit and discharge unit of the cathode electrode. A fuel cell characterized by being processed.