JPS6023977A - Fuel cell - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a methanol-air acidic electrolyte fuel cell, and particularly to a fuel cell of the all-position type fuel cell used as a power source for home appliances. A fuel 7 with an oxygen-enriching gas separation membrane is associated with the pond.

[Background of the invention]

The oxidant gas used in conventional fuel cells has generally been air or oxygen. It is generally known that in order to increase the efficiency of a fuel cell, it is sufficient to increase the oxygen partial pressure at the air electrode. Generally, in order to increase the oxygen partial pressure in a battery, the entire battery is placed in a high-pressure tank, and the pressure inside the battery is increased while maintaining the pressure balance between the fuel and the oxidizer. This method can be applied to large-capacity fuel cells for industrial or electric power use. On the other hand, for small-capacity fuel cells such as those used in home appliances, increasing the oxygen partial pressure using the method described above is not practical, and a new method must be developed.

In the case of methanol fuel cells, since the fuel is liquid, there are no reports on methods for increasing the partial pressure of oxygen in the air.

On the other hand, the demand for gas separation membranes is increasing for medical purposes and combustion furnaces, and the former has been put into practical use in the United States, where air with an oxygen concentration of 40% can be obtained from 4 to 8 times per minute.

In order to obtain 40% oxygen-enriched air using a gas separation membrane, the permeability coefficient ratio (Po2/PN2) must be 2.7 or more. Film materials that satisfy this value include polyphenylene oxide (Po2/PN2=4.3) and ethyl cell 0-'-(P02/PN2=3.4).
) There are membranes, etc.

- In order to increase the efficiency of fuel cells, it is sufficient to increase the oxygen partial pressure, and for this purpose, the purpose can be achieved by using oxygen-enriched air by a gas separation membrane as an oxidizing agent, and it will be highly effective. becomes possible.

[Purpose of the invention]

An object of the present invention is to improve cell performance that leads to cost reduction as a step in applying a methanol fuel cell to an all-position fuel cell as a power source for home appliances. That is, in a methanol fuel cell that uses air as an oxidizing agent, by disposing a gas separation membrane on the air supply side, the oxygen partial pressure in the air is increased and the performance of the cell is improved.

[Summary of the invention]

It is generally known that in order to improve the performance of the air electrode of a fuel cell, it is sufficient to increase the oxygen partial pressure in the oxidant gas. To achieve this goal, the entire battery must be made to have a high voltage. However, when it comes to home appliances, it is difficult to put them into practical use due to initial costs, packaging, etc.

Recently, research on single-select gas separation membranes has become active, and oxygen enrichment (
Using membranes (separation), it has become possible to obtain air enriched with more than 40% oxygen.

The present invention provides oxygen-enriched air by installing this oxygen-enriching membrane on the oxidant gas (air) side of a fuel cell, thereby improving the stain pond performance.

[Embodiments of the invention]

Examples of the present invention will be described below; however, the present invention is not limited to these examples in any way.

Example 1 A mixture of an electrode catalyst carrying 15 wt% of platinum, Polyflon dispersion liquid (manufactured by Daikin Industries), and water was mixed with carbon, which is a conductive porous base material, by a wet reduction method using an acetylene black carrier. After applying it to paper, in the air,
An air electrode was obtained by firing for 300'c-0.5h.

The amount of polytetrafluoroethylene water repellent added in the air electrode was 2Qwt% based on the air electrode catalyst layer. Moreover, the amount of platinum is 0.9 mg/cm2.

Kono air electrode is 60℃-3mOI/l H2S 04
The current-potential characteristics were measured when air and pure oxygen were passed through the electrolyte as an oxidant gas, and the performance was evaluated. The measurement results are shown in Figure 1. As shown in Figure 1, when air is used as the oxidant gas, the current density is 0.8V v at a current density of 60mA/crn2.
A potential of 8N HE was shown. Furthermore, when pure oxygen was used as the oxidant gas, a potential of 0.88V was exhibited at the same current density.

In this way, by setting the oxygen partial pressure to 0.2 to 1.0, the potential of the air electrode is approximately 8 at a current density of 60 mA/cm''.
Improved by 0mV.

Example 2 Using the air electrode prepared in Example 1, when the oxygen partial pressure of the oxidant gas was changed, the current density that could be taken out at a constant air electrode potential was measured, and the results are shown in Figure 2. . In air electrode measurements, when the oxygen partial pressure in the oxidant gas is changed, the ratio of the maximum current density that can be extracted at a constant potential is ideally proportional to the oxygen partial pressure, as shown in Figure 2.3. do. However, when measured using the air electrode of Example 1, the current density ratio that can be extracted at an air electrode potential of 0.8 V shows a value lower than the ideal slope as shown in FIG. 24.

Using this measured value, assuming that 40% oxygen-enriched air is obtained with the oxygen-enriched membrane, when the air electrode potential is kept constant, the oxidant gas is approximately twice that of when air is used. current density can be extracted, and the performance of the air electrode is significantly improved.

Example 3 Air was passed through the oxygen enrichment membrane to the air electrode in Example 1 at a rate of about 35
When supplied as oxygen-enriched air, the current density obtained at 0.8 cm was 75 mA/ctn2. This value agreed well with the value of the curve in FIG. 23.

〔Effect of the invention〕

As described above, by using an oxygen-enriched membrane to make oxygen-enriched air in a fuel cell that uses air as an oxidant, the performance of the air electrode can be improved, which has a great effect on improving the efficiency of all-position fuel cells. There is.

[Brief explanation of the drawing]

FIG. 1 is a current-potential characteristic diagram of the air electrode, and FIG. 2 is a diagram showing the current density ratio that can be extracted at a constant air potential with respect to the oxygen partial pressure in the oxidizing gas. Agent Patent Attorney Akifuka Takahashi I Solid Density (@A〃-) $2 Oxygen Fi: (-) Continued from page 1 0 Inventor Kamo Tomo - 3-1-1 Saiwaimachi, Hitachi City No. Stock % Formula % 3-1-1 Saiwai-cho, Hitachi City, Hitachi Research Institute, Hitachi, Ltd.

Claims (1)

[Scope of Claims] 1. A fuel cell using a fuel and an oxidizing agent, and comprising an electrode and an electrolyte, characterized in that a gas separation membrane is used at the oxidizing gas inlet. 2. A fuel cell according to claim 1, characterized in that a gas or liquid is used as a fuel and air is used as an oxidizing agent. 3. A fuel cell according to claim 1, wherein the electrode comprises a conductive porous base material, an electrode catalyst, a water repellent, and a binder. 4. The fuel cell according to claim 1, wherein the electrolyte is an acidic or alkaline electrolytic solution or a matrix impregnated with these. 5. The fuel cell according to claim 1, wherein the gas separation membrane is an oxygen enrichment membrane. 6. A fuel cell according to claim 2, characterized in that hydrogen gas, natural gas, or steam reformed gas is used as the gaseous fuel, and hydrazine and methanol are used as the liquid fuel. 7. A fuel cell according to claim 3, characterized in that the conductive porous base material is a carbon porous plate made of a carbon material. 8. In claim 3, the fuel cell is characterized in that the electrode catalyst is made of conductive fine powder supporting an active metal. 9. In claim 3, the water repellent and binder is polyfluoroethylene. , polyethylene, BoIJ, x,
A fuel cell characterized in that V y is made of polypropylene and polymethyl methacrylate. 10. In claim 4, the electrolyte is phosphoric acid,
A fuel cell characterized in that sulfuric acid, trifluoromethanesulfonic acid, caustic alkali, or a matrix is a non-conductive material having ion exchange properties. 11. In claim 8, the conductive fine powder is graphite, furnace black/activated carbon. A fuel cell characterized in that it is made of tungsten carbide and tungsten bronze. 12. The fuel cell according to claim 8, wherein the active metal is at least one of Group 8 and Group 1 of the periodic table. 13. In claim 10, m) A fuel cell characterized by being an IJlux ion exchange membrane.