JPH0594832A - Solid high molecular electrolyte type fuel cell - Google Patents

Abstract

PURPOSE:To increase the reaction gas amount passing through a cell as well as to make it possible to operate the cell stably, by providing humidifiers in the loops of a fuel cell, and adding the steam to the reaction gas so as to maintain a solid high polymer electrolyte in a wetting condition constantly. CONSTITUTION:Recycle loops 7 and 8 are provided newly, and pumps 6 and 4 are provided in the loops 7 and 8. And a reaction gas recycled by the loops is led to a cell through humifiers 5, and in this case, the number of passing is made numerous, and the including amount of steam is increased to make it possible to feed a necessary amount of moisture. And the reflux ratio of the recycled reaction gas is set as desired in the relation with the output property of the cell. Although a bubbler is used as the humidifier, a steam generator, an ultrasonic humidifier, an internal humidifier, and the like can be used instead of the bubbler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte fuel cell, and more particularly to a solid polymer electrolyte fuel cell which maintains an optimum water content of the solid polymer electrolyte.

[0002]

2. Description of the Related Art A solid polymer electrolyte fuel cell is formed by disposing an anode or a cathode and an electrode base material on each of two main surfaces of a solid polymer electrolyte membrane. Each anode or cathode electrode is sandwiched between the solid polymer electrolyte membrane and the electrode base material. The solid polymer electrolyte membrane uses a polystyrene cation exchange membrane with sulfonic acid groups as the cation conductive membrane, a mixed membrane of fluorocarbon sulfonic acid and polyvinylidene fluoride, or trifluoroethylene grafted to the fluorocarbon matrix. However, recently, a perfluorocarbon sulfonic acid membrane has been used to extend the life of a fuel cell.

The solid polymer electrolyte membrane has a proton (hydrogen ion) exchange group in the molecule, and when it is saturated to contain water, it exhibits a specific resistance of 20 Ω · cm or less at room temperature and functions as a proton conductive electrolyte. The saturated water content changes reversibly with temperature. The electrode base material is a porous body and functions as a reaction gas supply means or a reaction gas discharge means of the fuel cell and a current collector. At the anode or cathode electrode, a three-phase interface is formed and an electrochemical reaction occurs.

At the anode, the reaction of the formula (1) occurs. H ₂ = 2H ⁺ + 2e (1) At the cathode, the reaction of the formula (2) occurs. 1 / 2O ₂ + 2H ⁺ + 2e = H ₂ O (2)

That is, at the anode, hydrogen supplied from outside the system produces protons and electrons. The generated protons move toward the cathode in the ion exchange membrane, and the electrons move to the cathode through an external circuit. On the other hand, in the cathode, oxygen supplied from the outside of the system reacts with protons moving from the anode in the ion exchange membrane and electrons moving from the external circuit to generate water.

In such a solid polyelectrolyte fuel cell, protons move in a hydrated state as they move from the anode to the cathode in the ion exchange membrane, so that the water content near the anode decreases and ion exchange occurs. The film dries. Therefore, it becomes difficult for protons to move near the anode unless water is supplied. When air is used as the oxidant, several times the theoretical consumption of air is sent, and the moisture in the ion-exchange membrane is carried out to the air, which causes the membrane to dry. In addition, solid polymer electrolyte fuel cells generally have 10
Since the operation is performed at a temperature near 0 ° C., water may evaporate and the ion exchange membrane may dry. For this reason, conventionally, a method has been adopted in which a fixed amount of water vapor, which is calculated as an appropriate amount, is replenished in the fuel gas and / or the oxidant gas and sent to the battery. As a general method of supplying steam, a method of bubbling a reaction gas through a bubbler maintained at a predetermined temperature is used.

FIG. 2 is a layout view showing a conventional solid polymer electrolyte fuel cell. The anode 1 and the cathode 3 are arranged on the solid polymer electrolyte membrane 2 to form a cell. Fuel gas is supplied to the anode 1 of this cell. An oxidant gas is supplied to the cathode 3 of the cell. Both the reaction gas of the fuel gas and the oxidant gas are supplied to the respective reaction gas supply systems 11, 12
Supplied through. A humidifier 5 which is a bubbler is provided in each of the reaction gas supply systems. Both reaction gases that have passed through the cell are discharged through the respective reaction gas discharge systems 9 and 10.

[0008]

However, in the above-mentioned conventional method, the reaction gas is passed through the bubbler only once, and the amount of replenishment of steam to the reaction gas is insufficient, and after a long time operation, There is a problem that the film becomes dry and the battery performance is deteriorated. When it is in a dry state, the electric resistance of the film increases and the cell characteristics deteriorate. The present invention has been made in view of the above points, and an object thereof is to provide a solid polymer electrolyte fuel cell which is excellent in reliability by sufficiently supplementing water vapor into a reaction gas without deterioration of cell characteristics.

[0009]

The above-mentioned object has a cell, a reaction gas supply system, a reaction gas discharge system, a humidifier, and a recycle loop, and the cell comprises a solid polymer electrolyte membrane, an anode and a cathode. The reaction gas supply system supplies reaction gas to the cell through a humidifier,
The reaction gas exhaust system is for exhausting the reaction gas that has passed through the cell, and the recycle loop is a circuit for returning the exhausted reaction gas of the reaction gas exhaust system to the cell again, and a humidifier is provided in the loop. The humidifier is achieved by adding steam to the reaction gas.

[0010]

The reaction gas returning to the recycle loop already contains water vapor, and the water vapor content in the reaction gas can be increased by passing it through the humidifier again.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a layout view showing a solid polymer electrolyte fuel cell according to an embodiment of the present invention. The layout of the conventional solid polymer electrolyte fuel cell is different from the recycle loops 7 and 8.
Is different. Pumps 4 and 6 are provided in each recycling loop. The reaction gas to be recycled is introduced into the cell through the humidifier 5. Since the reaction gas to be recycled passes through the humidifier a number of times, it has a large water vapor content and can replenish the cell with a necessary amount of water. The reflux ratio of the reaction gas to be recycled can be arbitrarily set in relation to the output characteristics of the cell.

In the above example, a bubbler is used as the humidifier, but a steam generator, an ultrasonic humidifier, an internal humidifier, etc. can be used together with the recycle loop in addition to the bubbler. Further, although not shown, if the pump 6 or 4 is driven by a conductivity type signal for detecting the dry state of the cell to control the amount of recycled reaction gas, the amount of water in the polymer electrolyte in the cell can be maintained in an optimum state. Can also

[0013]

The present invention has a cell, a reaction gas supply system, a reaction gas discharge system, a humidifier, and a recycle loop. The cell is a solid polymer electrolyte membrane with an anode and a cathode. The gas supply system supplies the reaction gas to the cell through the humidifier, the reaction gas discharge system discharges the reaction gas that has passed through the cell, and the recycle loop is the reaction of the discharged reaction gas discharge system. It is a circuit that returns gas to the cell again, and a humidifier is provided in the loop.Since the humidifier adds water vapor to the reaction gas, the solid polymer electrolyte is always kept in a wet state and stable battery operation is possible. It will be possible. Further, in the battery of the present invention, the total amount of the reaction gas passing through the cell can be made larger than that in the conventional battery, so that the equidistributed property of the reaction gas can be improved, and further the temperature distribution inside the cell can be improved. Can be smaller.

[Brief description of drawings]

FIG. 1 is a layout view showing a solid polymer electrolyte fuel cell according to an embodiment of the present invention.

FIG. 2 is a layout view showing a conventional solid polymer electrolyte fuel cell.

[Explanation of symbols]

 1 Anode 2 Solid Polymer Electrolyte 3 Cathode 4 Pump 5 Humidifier 6 Pump 7 Recycle Loop 8 Recycle Loop 9 Reactive Gas Exhaust System 10 Reactive Gas Exhaust System 11 Reactive Gas Supply System 12 Reactive Gas Supply System

Claims (3)

[Claims] 1. A cell comprising a cell, a reaction gas supply system, a reaction gas discharge system, a humidifier, and a recycle loop, wherein the cell comprises a solid polymer electrolyte membrane and an anode and a cathode. The gas supply system supplies the reaction gas to the cell via the humidifier, the reaction gas discharge system discharges the reaction gas that has passed through the cell, and the recycle loop the reaction of the discharged reaction gas discharge system. A solid polymer electrolyte fuel cell characterized in that it is a circuit for returning gas to the cell again, and a humidifier is provided in the loop, and the humidifier adds water vapor to the reaction gas. 2. The solid polymer electrolyte fuel cell according to claim 1, wherein the humidifier is a bubbler. 3. The solid polymer electrolyte fuel cell according to claim 1, wherein the humidifier in the reaction gas supply system and the humidifier in the recycle loop are the same.