Patent ID: 8206877

Claim:
A membrane electrode assembly for a polymer electrolyte fuel cell, comprising: an ion conducting membrane having two sides in a thickness direction thereof; a porous anode catalyst layer that is laminated on one side of the ion conducting membrane and that has an anode catalyst that accelerates anode reaction; a porous cathode catalyst layer that is laminated on the other side of the ion conducting membrane and that has a cathode catalyst that accelerates cathode reaction; an anode diffusion layer that is laminated on an outer side of the anode catalyst layer and that allows an anode fluid to pass therethrough; and a cathode diffusion layer that is laminated on an outer side of the cathode catalyst layer and that allows a cathode fluid to pass therethrough, wherein the anode catalyst in the anode catalyst layer contains a poisoning-suppression catalytic component, including at least one of ruthenium, tin, osmium, rhodium, palladium, nickel, copper, cobalt, manganese, zinc, iridium, and iron, that reduces poisoning of carbon monoxide contained in the anode fluid, the anode catalyst layer includes a first catalyst layer portion and a second catalyst layer portion, the first catalyst layer portion is located closer to the anode diffusion layer than the second catalyst layer portion, and the second catalyst layer portion is located closer to the ion conducting membrane than the first catalyst layer portion, the density of the first catalyst layer portion is smaller than the density of the second catalyst layer portion, the pore diameter of the first catalyst layer portion is smaller than the pore diameter of the second catalyst layer portion, and wherein the anode fluid flows from an upstream side of the anode catalyst layer toward a downstream side of the anode catalyst layer, and the amount of poisoning-suppression catalytic component supported per unit area is increased from the upstream side of the anode catalyst layer to the downstream side of the anode catalyst layer.