JPS58166658A - Fuel cell - Google Patents

Abstract

PURPOSE:To equalize current distribution, by both gradually narrowing construction of a groove used as the fuel passage from an inlet side to an outlet side and reversely gradually widening an air passage to eliminate a pressure difference between fuel and air in an electrode base plate. CONSTITUTION:A catalytic layer 6 and grooves 4, 4' are formed to each one side of porous electrode base plates 1, 1'. The groove 4 is passage for hydrogen and the groove 4' is an air passage formed to a shape crossing at a right angle with said hydrogen passage. A width of the hydrogen passage passing through at least one of these grooves is formed to be provided such that the inlet side is, for instance, two times the outlet side. In this way, a pressure difference between fuel and air in the electrode base plate can be eliminated, while current distribution can be equalized.

Description

[Detailed description of the invention] Book! II@ relates to a fuel cell equipped with a porous gas diffusion electrode, and relates to a fuel cell having a structure in which an optimum St is provided on one side of the porous gas diffusion electrode to form a passage for fuel or air.

Conventionally, in a gas diffusion electrode of the present invention, in which a groove is provided on one side of a porous substrate, this groove is used as a passage for fuel or air, and a 1iiiVc catalyst layer is provided on the opposite side, the groove has a width as shown in 11iJK. , the depth was constant at 4, the first
In the figure, 1 is a porous gas diffusion electrode substrate, and 2 is a groove for fuel and air passages.

When this wrinkled electrode substrate is used, because the passage for 1 pF of fuel or air is provided at the same flow rate from the population side to the outlet side, these gases are gradually consumed by electrochemical reactions as they flow through the passage gate. Alternatively, there is a problem in that the pressures of these gases in the passages vary as water is produced. In other words, the pressure of the gas gradually decreases or decreases from the passage side toward the exit 1i1, and due to this phenomenon, (1) the pressure difference between the fuel and air becomes large, and the pressure inside the battery increases. (2) Because the fuel and air pressures differ locally, the electrochemical reaction rate differs, and the current distribution on the electrode substrate becomes large. .

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art, namely the pressure distribution of fuel and air within the electrode substrate, and to provide a fuel cell with improved performance.

The key point of the present invention is that the structure of the groove, which serves as a fuel passage, is gradually narrowed from the inlet to the outlet side, while the air passage, on the contrary, is gradually widened.

By adopting this structure, the flow velocity of fuel and air is always kept constant on the electrode substrate.

The specific structure of the habit is that (1) the width of the groove gradually narrows from the population side toward the exit, and (2) the depth of the groove gradually decreases from the entrance side to the exit side. This is effective for the fuel passage, and since water is produced in the air passage, it is effective to reverse it. In addition to the above methods (1) and (2), in order to eliminate the difference in electrochemical reaction rate caused by the distribution of gas pressure to be supplied, that is, the current distribution, from the gas population side to the outlet side, It is also effective to increase the porosity of the electrode substrate on the fuel side and conversely decrease it on the air side.

Book @ Ming may use any of these methods.

Examples of the present invention will be described below.

Example (1) A fuel cell was manufactured using hydrogen as a fuel and air as an oxidizing agent under conditions such that 50% of each of hydrogen and oxygen in the air was consumed within the cell. As shown in FIG. 2, the hydrogen passage #I3 was provided so that the inlet side was twice as large as the outlet side. For the air passage, grooves were formed in another porous electrode substrate so that the inlet side was 1.5 times as wide as the outlet side, and carbon was formed on the two electrode substrates by a known method. An electrode catalyst layer supporting a small amount of platinum is provided on the wafer, and an electrolyte made of silicon carbide impregnated with phosphoric acid is sandwiched between the electrode catalyst layer and the unit cell shown in Fig. 3. In Figure 3, 1
and 1' are porous electrode substrates, each of which has a catalyst layer 6 and #lI4.4' formed on one side. #I4 is a hydrogen passage, and 4' is an air passage perpendicular to this hydrogen passage. 5 is an electrolyte, 7 is a graphite plate, 8 is an insulating plate, 9 is an end plate for tightening, 10 is a bolt for tightening, 11
is a nut for tightening. A hydrogen manifold and an air manifold were attached to each O battery to form a battery.

5 () During OA power generation, we measured the population and outlet pressures of hydrogen and air, and examined the differential pressures of each.We found that both pressures were constant, with no difference between the population side and the outlet side. Furthermore, no gas cross occurred within the battery.

Example (2) Similarly to the conventional method, as shown in FIG. 1, grooves that serve as passages for hydrogen and gas are provided on one side of a porous electrode plate with the same width. However, the depth of the groove was sloped so that the inlet side of the hydrogen passage was twice as deep as the outlet side, and the depth of the groove was 1.5 times the population - on the outlet side of the air passage. Next, a catalyst layer was provided on these electrode substrates, and a battery was assembled in the same manner as shown in FIG.
The gas pressures at the inlet and outlet of the hydrogen and air grooves during manual power generation were measured, but as in Example (1), no differential pressure was observed.

Example (3) Grooves that serve as passages for hydrogen and air are the same as the conventional #! The porosity of the electrode substrate was gradually changed so that on the fuel side, the porosity was 40% on the inlet side and 80% on the outlet side. In addition, on the air side, the population side was changed to 80% and the exit side to 53%. The following battery as shown in FIG. 13 was made using this electrode substrate gold, and the electric ratio distribution on the electrode surface when the terminal '1 was discharged at a current of 500 A was found to be almost the same in all n parts.

As is clear from the above examples, eζ, according to the present invention,
It is possible to eliminate the pressure difference between fuel and air within the electrode substrate, and it is also possible to make the warm current distribution uniform. Therefore, it can be said that the present invention has extremely great industrial value.

[Brief explanation of the drawing]

Figure 1 shows that # is set using the conventional method to achieve porosity 'I! Figure 2 is a perspective view of a porous electrode substrate provided with #ll according to the present invention, and male 3bIA is the next fuel used in the present invention.
I11? t1! FIG. l... Porous gas diffusion electrode substrate, 2... Groove, 3...
・Groove, 4.4'... Screen, 5... Electrolyte, 6... Catalyst layer, 7... Graphite plate, 8... Insulating plate, 9... End plate for tightening, 10...Continued from page 1 ■Applicant Hitachi Chemical Co., Ltd. 2-1-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo

Claims (1)

[Scope of Claims] 1. A pair of porous gas diffusion electrodes and an electrolyte holding matrix disposed between the electrodes, one of the electrodes F
i. A fuel cell having a fuel supply groove and the other electrode having an air supply groove, such that the flow rate of the fuel or air through at least one of the grooves is substantially constant from the population side to the outlet side. A fuel cell characterized by having a groove shape. 2. The fuel cell according to claim 1, characterized in that the width of the fuel supply groove gradually narrows from the fuel inlet side to the outlet side. & Claims] A fuel cell according to @1lil, characterized in that the depth of the fuel supply groove gradually becomes shallower from the fuel inlet side to the a-port side. 4. The fuel cell according to claim 1, wherein the porosity of the porous gas diffusion electrode having the fuel supply groove is gradually increased from the fuel inlet side to the fuel outlet side. & In claim i81, paragraph 1, the width of the air supply groove gradually increases from the air intake side to the outlet side! 11 fuel cells. 6. The fuel cell according to claim 1, wherein the depth of the air supply groove gradually becomes deeper from the air intake side to the outlet side. 7. The fuel cell according to claim 1, wherein the pores of the porous gas diffusion electrode having the air supply groove gradually become smaller from the air inlet side to the outlet side.