Patent ID: 7794863

Claim:
A proton exchange membrane fuel cell comprising: unit cells that respectively include an electrolyte membrane, and a fuel electrode, using hydrogen gas as a fuel, and an air electrode, using air as an oxidizer, provided on respective surfaces of the electrolyte membrane; mixing means for introducing water to an air feed to the air electrode; and a separator interposed between the unit cells, the separator and the unit cells being stacked to form the fuel cell in which a mixed fluid of air and water is supplied to the air electrode of each unit cell through the separator, wherein the separator includes an expanded metal sheet formed into a corrugated plate provided with thin projecting portions, serving as a current collector, through which the mixed fluid can pass, the expanded metal sheet being in contact with the air feed and with an electrode diffusion layer of the air electrode, droplets of water adhering to and evaporating from a surface of the expanded metal sheet to provide latent heat cooling; wherein flat top surfaces of the thin projecting portions of the expanded metal sheet are in contact with the electrode diffusion layer at the air electrode; wherein base portions between the thin projecting portions of the expanded metal sheet are in contact with a separator base; and wherein a hydrophilic treatment is applied to the expanded metal sheet so that the water droplets are better retained on the expanded metal sheet.