JPH10270063A - Phosphatic fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphatic fuel cell with a proper gas sealing performance and assemble a low-cost carbon paper and electrode base materials therein with higher reliability at lower cost by having small holes in gas distribution groove impregnated with zirconium oxide and permeated with phosphoric acid. SOLUTION: Small holes in areas located at both side ends of distribution grooves in a fuel pole carbon paper 6 to carry a fuel pole catalytic layer 12 and form a fuel electrode, an air pole carbon paper to carry an air pole catalytic layer 13 and form an air electrode, a fuel pole base material 3 provided with fuel gas distribution grooves 9 and an air pole base material 4 provided with air distribution grooved 10 are impregnated with zirconium oxide and then permeated with phosphoric acid to produce zirconium phosphate. In this way, end seals 23, 24, 21, 22 are provided with gas sealing performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphoric acid fuel cell using phosphoric acid as an electrolyte, and more particularly to a seal structure for preventing gas leakage from an end of a single cell.

[0002]

2. Description of the Related Art FIG. 4 is an exploded perspective view showing a basic structure of a phosphoric acid fuel cell. A single cell 1, which is a basic unit, comprises a matrix 2 holding phosphoric acid, a porous fuel electrode carbon paper 6 supporting a catalyst, a porous air electrode carbon paper 7 also supporting a catalyst, and a fuel gas flow groove 9. A fuel electrode base material 3 made of porous carbon provided with an air electrode carbon base material 4 made of the same porous carbon provided with an air flow groove 10 arranged orthogonally to the fuel gas flow groove 9. Have been. A single cell 1 is alternately stacked with a separator 5 made of a gas-impermeable material, and a cooling plate 8 for removing heat generated by power generation and maintaining the temperature of the single cell at an appropriate temperature is appropriately interposed, and the fuel cell main body is provided. Are formed.

The fuel gas sent to the fuel gas flow groove 9 and the air sent to the air flow groove 10 pass through the porous fuel electrode carbon paper 6 and air electrode carbon paper 7, respectively, It reaches the layer and causes an electrochemical reaction, so that electric energy is extracted between the two electrodes. Since the power generation voltage of one single cell is a low voltage of less than 1 V, as shown in the figure, the single cells are stacked to be electrically connected in series and configured to generate a required voltage. .

[0004]

In the above configuration,
The fuel gas passes through the inside of the porous anode carbon paper 6 or the porous anode base material 3 and leaks from the side surface, or the air is the porous cathode carbon paper 7 or the porous cathode base material. If the fuel gas permeates through the inside of the fuel cell 4 and leaks from the side surface, a direct reaction between the fuel gas and the air occurs, thereby deteriorating the characteristics of the fuel cell and possibly causing damage. The end portions of the electrode carbon paper 7, the fuel electrode substrate 3, and the air electrode substrate 4 need to have a gas seal structure.

In a conventional phosphoric acid type fuel cell, the gas seal structure at the end portion is, for example, a method of coating a gas-impermeable membrane such as a polytetrafluoroethylene sheet, or a gas-tight structure inserted between single cells. There is a structure that incorporates a gas impermeable material such as a method in which both ends of a permeable separator are formed in a bank shape to cover the ends of the carbon paper and the electrode base material. Carbon powder or S, for example, in the pores at the end of the electrode substrate
A so-called wet seal type structure is used in which a phosphoric acid-resistant ceramic powder such as iC is impregnated to improve the ability to retain a phosphoric acid solution to seal gas. Of these, the former structure incorporating a gas-impermeable material has the advantage of obtaining a configuration excellent in gas sealing properties, but has the disadvantage that the number of manufacturing steps is increased and the material cost is increased. On the other hand, in the latter structure of the wet sealing method, the number of manufacturing steps and material cost can be kept low, but the fine pores are impregnated with powder in the fine pores, and the surface tension of the permeated phosphoric acid is reduced. Since the sealing is intended, the sealing performance depends on the size and uniformity of the holes, and there is a problem that a reliable seal is not always guaranteed.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to produce carbon paper and an electrode base material whose ends maintain proper gas sealing performance, and to reduce the number of manufacturing steps. It is an object of the present invention to provide a highly reliable and inexpensive phosphoric acid fuel cell which can be manufactured without increasing the material cost.

[0007]

In order to achieve the above object, according to the present invention, a catalyst is supported on porous carbon paper on both main surfaces of a flat matrix holding phosphoric acid as an electrolyte. A fuel electrode and an oxidant electrode,
Further, a phosphoric acid-type fuel formed by stacking a plurality of single cells formed by arranging an electrode substrate made of porous carbon having gas flow grooves for supplying fuel gas or air to both outer surfaces thereof In the battery, in the pores of the regions located on both sides of the gas flow grooves of the carbon paper and the electrode substrate, for example, the end of the carbon paper, or the end of the electrode substrate is placed in a slurry solution of zirconium oxide. The zirconium phosphate is formed by a method of impregnating zirconium oxide into the pores by dipping, drying, and then infiltrating phosphoric acid.

As described above, if the phosphoric acid is impregnated after impregnating the pores with zirconium oxide, the zirconium oxide reacts with phosphoric acid to generate zirconium phosphate. At this time, since volume expansion occurs to fill the pores of the pores, gas permeation is prevented and gas sealing properties are ensured. In particular, in a phosphoric acid type fuel cell, carbon paper and zirconium oxide are impregnated in advance in pores in both end regions of the electrode substrate, and phosphoric acid used as an electrolyte during cell assembly is impregnated. Since zirconium phosphate can be produced, gas sealability can be ensured by a simple operation process.

[0009]

FIG. 1 is an exploded perspective view of an essential part of a single cell showing an embodiment of a phosphoric acid fuel cell according to the present invention. In this configuration, a porous fuel electrode carbon paper 6 carrying an anode catalyst layer 12 and a porous air electrode carbon paper carrying an air electrode catalyst layer 13 are provided on both sides of a matrix 2 holding phosphoric acid. And a fuel electrode base 3 made of a porous carbon material having a fuel gas flow groove 9 and an air electrode base made of the same porous carbon material provided with an air flow groove 10 on both outer surfaces thereof. The material 4 is arranged to form a single cell.

Particularly, in this configuration, both end portions of the fuel electrode base material 3 and the fuel electrode carbon paper 6 which are located outside the fuel gas flow grooves 9, that is, the fuel electrode base material end seal portions 2.
1 and the end portion 23 of the fuel electrode carbon paper, and both end portions located outside the air flow groove 10 of the air electrode base material 4 and the air electrode carbon paper, ie, the end portion 22 of the air electrode base material. And the air electrode carbon paper end seal portion 24 are both formed by impregnating zirconium oxide into the pores. At the time of assembling the cell, phosphoric acid is penetrated into these portions and left at 80 to 100 ° C. It is characterized by reacting zirconium oxide with phosphoric acid to produce zirconium phosphate.

FIG. 2 is a process diagram showing a procedure for generating zirconium phosphate in the pores of each end seal portion of the single cell shown in FIG. FIGS. 3A and 3B are microscopic views of the results of microscopic observation of the structure of the fuel cell substrate end end seal portion 21 of the single cell shown in FIG. 1, wherein FIG. 3A is a schematic view of the structure after impregnation with zirconium oxide, and FIG. Is a histological diagram after phosphoric acid has been successively infiltrated.

As shown in FIG. 2, when zirconium phosphate is generated in the pores of each end seal portion, first, the particle diameter is 5 to 5.
100 μm zirconium oxide powder is mixed with alcohol and water to form a slurry, and the electrode substrate or the end of carbon paper is immersed in the slurry to impregnate the zirconium oxide into the porous pores. Subsequently, the slurry is taken out of the slurry and the excess slurry on the surface is wiped and dried.
FIG. 3A shows the organization corresponding to this point.
It can be seen that zirconia oxide powder 34 is impregnated in the pores of the porous carbon formed by binding the carbon fibers 31 and the carbon particles 32 with the pitch binder 33.

The impregnation with phosphoric acid is performed simultaneously with the matrix in the cell assembling process, the electrode base material, and the carbon paper in the phosphoric acid impregnating process. 80-10 after impregnation with phosphoric acid
When cured at 0 ° C., phosphoric acid and zirconium oxide react to produce zirconium phosphate. FIG. 3 (b)
Indicates a structure corresponding to this point, and the zirconia oxide powder 34 reacts with phosphoric acid to produce zirconium phosphate 3
5 has been generated. Since zirconium phosphate 35 is a clayey material having viscosity and is a hydrolyzate, it is produced in a state in which the volume expands during the reaction and plugs the space in the pores.
In the portion where the zirconium phosphate 35 is generated, diffusion of gas is prevented, and good sealing performance is obtained.

Therefore, as shown in FIG.
In a single cell in which zirconium phosphate is generated in the space in the pores at both ends of each carbon paper, leakage of fuel gas and air from both sides is effectively prevented,
It will be able to operate stably.

[0015]

As described above, according to the present invention, the fuel electrode and the oxidant electrode each having a catalyst supported on porous carbon paper are provided on both main surfaces of a flat matrix holding phosphoric acid as an electrolyte. A single cell formed by arranging an electrode substrate made of porous carbon having a gas flow groove for supplying fuel gas or air to both outer surfaces thereof,
In a phosphoric acid type fuel cell composed of a plurality of layers, for example, the end of the carbon paper or the electrode substrate The end of the material is immersed in a slurry solution of zirconium oxide to impregnate the pores with zirconium oxide,
Since zirconium phosphate is formed by a method of infiltrating phosphoric acid after drying, carbon paper and a carbon base material having proper gas sealing performance at the ends increase production man-hours and material costs. Therefore, a phosphoric acid type fuel cell which is excellent in reliability and inexpensive can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a main part of a single cell showing an embodiment of a phosphoric acid fuel cell of the present invention.

FIG. 2 is a process diagram showing a procedure for generating zirconium phosphate in pores of each end seal portion of the single cell shown in FIG.

3A and 3B are schematic views of microstructure observation results of the structure of the fuel cell base material end seal portion 21 of the single cell shown in FIG. 1, wherein FIG. 3A is a schematic view of the structure after impregnation with zirconium oxide, and FIG. Histology after subsequent phosphoric acid infiltration

FIG. 4 is an exploded perspective view showing a basic configuration of a phosphoric acid type fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single cell 2 Matrix 3 Fuel electrode base material 4 Air electrode base material 6 Fuel electrode carbon paper 7 Air electrode carbon paper 9 Fuel gas flow groove 10 Air flow groove 12 Fuel electrode catalyst layer 13 Air electrode catalyst layer 21 Fuel electrode base Material end seal part 22 Air electrode base material end seal part 23 Fuel electrode carbon paper end seal part 24 Air electrode carbon paper end seal part 31 Carbon fiber 32 Carbon particles 33 Pitch binder 34 Zirconium oxide powder 35 Zirconium phosphate

Claims (2)

[Claims] 1. A fuel electrode comprising a catalyst supported on porous carbon paper and an oxidant electrode are disposed on both main surfaces of a flat matrix holding phosphoric acid as an electrolyte, and a fuel gas is disposed on both outer surfaces thereof. Alternatively, in the phosphoric acid type fuel cell configured by stacking a plurality of single cells formed by arranging an electrode substrate made of porous carbon having a gas flow groove for supplying air, the carbon paper A phosphoric acid-type fuel cell characterized in that zirconium phosphate is formed in pores in regions located at both end portions of the gas flow groove with the electrode substrate. 2. The zirconium phosphate in the pores is impregnated with zirconium oxide in the pores by immersing the end of the carbon paper or the end of the electrode substrate in a slurry solution of zirconium oxide and dried. The phosphoric acid type fuel cell according to claim 1, wherein the phosphoric acid fuel cell is formed by infiltrating post-phosphoric acid.