JPH0129308B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel cell, and particularly to the structure of an electrode portion thereof.

A conventional fuel cell of this type is shown in FIG. In the figure, reference numeral 1 denotes a gas separation plate, and a fuel flow path 2 and an oxidizer flow path 3 are provided on both sides of the plate. 4
is a fuel electrode, in contact with which is an electrolyte matrix 5, and above which is an oxidizer electrode 6. 7 is packing for sealing, and 8 is an electrolyte reservoir provided around the gas separation plate 1 to hold electrolyte. The parts marked with a in each number are the parts where the battery reaction occurs, and the part numbered 6 is the sealed part, which is treated to be air-impermeable.

Next, the operation will be explained. The fuel supplied from the fuel flow path 2 is oxidized at the fuel electrode 4, hydrogen becomes cations and electrons, and the cations move through the reaction part 5a of the electrolyte matrix 5 and reach the oxidizer electrode 6, where the oxidizer flow It reacts with the oxidizing agent supplied from path 3 to produce water. The electrons generated at the fuel electrode 4 pass through an external load (not shown) and reach the oxidizer electrode 6, where they contribute to a reduction reaction and become electrical energy in the external load. During the reaction, the electrolyte matrix 5 must always hold electrolyte,
For this purpose, an electrolyte reservoir 8 is used as an electrolyte reservoir.
is provided. In order to supply the electrolyte from the electrolyte reservoir 8 to the electrolyte matrix 5 and to seal the gas, the peripheral portion 4b of the electrode 4 is treated to be hydrophilic in order to allow the electrolyte to penetrate therein.

Since the conventional fuel cell is constructed as described above, there is a problem in that the electrolyte permeates from the hydrophilic peripheral portion 4b of the electrode 4 into the central reaction portion 4a of the electrode 4. The central reaction part 4a of the electrode 4 is
Water-repellent treatment is applied using PTFE (polytetrafluoroethylene), but if the water-repellent treatment is applied too strongly, the pores in the electrode base material will be filled, resulting in poor gas permeability, making it difficult to function as a gas diffusion electrode. is damaged. When the electrolyte permeates from the peripheral portion 4b of the electrode 4 into the central reaction portion 4a in this way, gas permeability deteriorates, resulting in a disadvantage that the function as a gas diffusion electrode is impaired.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it makes the peripheral part of the electrode facing the electrolyte reservoir hydrophilic, and
By providing a portion between the hydrophilic peripheral portion of the electrode and the central reaction portion that is more water repellent than the central reaction portion, electrolyte movement from the hydrophilic peripheral portion of the electrode to the central reaction portion is suppressed; The purpose is to maintain the normal reaction of the fuel cell.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of a fuel cell according to the present invention. In the figure, numerals 4 and 6 are a fuel electrode and an oxidizer electrode, respectively, which are carbon paper with a thickness of 400 to 500 μm coated with a catalyst layer. 4b is the peripheral part of the fuel electrode 4 with an average particle size of 1 to
It is filled with fine silicon carbide particles of about 5 μm.
Reference numeral 9 denotes a central reaction portion 4 provided between this electrode peripheral portion 4b and the central reaction portion 4a coated with a catalyst.
This part is more water repellent than A, and is a layer with a width of 5 to 15 mm, and is obtained by mixing a larger amount of PTFE than the central reaction part.

Electrolyte must be sufficiently retained in the electrode peripheral portion 4b for gas sealing, but if the electrolyte moves to the adjacent central reaction portion 4a, the gas diffusivity of the central reaction portion 4a will deteriorate and the electrode function will deteriorate. Therefore, by providing a boundary layer 9 having strong water repellency between the electrode peripheral part 4b and the central reaction part 4a, which serves as a gas seal, the electrolyte contained in the electrode peripheral part 4b is prevented from flowing into the central reaction part 4a. Movement can be suppressed. in general,
The carbon paper that is the electrode base material of the electrode reaction part 4a is appropriately water-repellent treated, which reduces the intrusion of the electrolyte from the electrolyte matrix 5 through the catalyst layer, which also has some water repellency. However, applying too strong a water repellent treatment will impair gas permeability and the electrode 4
This is not done because it inhibits the reactivity of a. In this sense, the conventional structure cannot sufficiently deal with the intrusion of electrolyte from the electrode peripheral part 4b into the central reaction part 4a. Layer 9 is important.

In the above embodiment, the oxidant electrode 6 uses the packing 7 as a gas seal, but it is also possible to use a gas seal filled with electrolyte in the same way as the fuel electrode 4, in which case the oxidant electrode 6 as well, a portion 9 that is more water repellent than the central reaction portion 6a may be provided between the central reaction portion 6a and the gas seal portion. Further, in this case, the fuel electrode 4 may be gas-sealed using packing.

As described above, according to the present invention, the peripheral part of the electrode facing the electrolyte reservoir is made hydrophilic, and the area between the hydrophilic peripheral part of the electrode and the central reaction part is more water repellent than the central reaction part. The provision of this section has the effect of suppressing the movement of electrolyte from the hydrophilic peripheral area of the electrode to the central reaction area, thereby sustaining the normal reaction of the fuel cell.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the main parts of a conventional fuel cell, and FIG. 2 is a cross-sectional view showing the main parts of a fuel cell according to the present invention. In the figure, 1 is a gas separation plate, 4 is a fuel electrode,
4a is a central reaction part, 4b is a peripheral part, 5 is an electrolyte matrix, 6 is an oxidizing agent electrode, 8 is an electrolyte reservoir, and 9 is a part more water repellent than the central reaction part 4a. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a fuel cell configured by sequentially stacking a gas separation plate, a fuel electrode, an electrolyte matrix, and an oxidizer electrode with an electrolyte reservoir in the peripheral part, the peripheral part of the electrode facing the electrolyte reservoir is made hydrophilic, and , A fuel cell characterized in that a portion more water repellent than the central reaction portion is provided between the hydrophilic peripheral portion of the electrode and the central reaction portion.