SOLID POLYMER ELECTROLYTE FUEL CELL

PROBLEM TO BE SOLVED: To increase the output of a fuel cell by using a solid polymer electrolyte film in which the water content on the negative electrode side is higher in the thickness direction than the water content on the positive electrode side. SOLUTION: The water content of a solid polymer electrolyte film of a solid polymer electrolyte fuel cell is made uneven in the thickness direction, continuously varied in the thickness direction, is made the highest on the side coming in contact with a negative electrode, and the lowest on the side coming in contact with a positive electrode, and as a result the solid polymer electrolyte film is made water repellent. The reverse diffusion of water from the positive electrode for replenishing decrease in water content in the negative electrode efficiently occurs, excess wetting of the positive electrode is prevented to make efficient catalytic action possible, and as a result, the output of the fuel cell is increased. As the solid polymer electrolyte film, for example, an ethylene- tetrafluoroethylene copolymer film is used, and by applying the specified treatment to the film, the water content on one surface is maximized to about 86 wt.%, and continuously decreased in the film thickness direction.