An electrode for a solid polymer fuel cell includes a gas diffusion layer, an electrode catalyst layer disposed between a solid polymer membrane of the fuel cell and the gas diffusion layer, and a water-holding layer disposed between the gas diffusion layer and the electrode catalyst layer. Under high-relative humidity conditions of reaction gases, flooding can be prevented because the electrode catalyst layer is made porous, while under low-relative humidity conditions of reaction gases, sufficient water contents can be stably provided thanks to the water-holding layer so that proton conductivity of the solid polymer membrane can be maintained appropriately. Consequently, high-performance and high-durability electrode and membrane electrode assembly for a solid polymer fuel cell can be provided such that the performance and the durability thereof are not affected by change in relative humidity in reactant gases supplied to the solid polymer fuel cell.
In a polymer electrolyte fuel cell in which a cathode diffusion layer, a cathode electrode catalyst layer, a polymer electrolyte membrane, an anode electrode catalyst layer, and an anode diffusion layer are laminated in this order, electron conductivity of the cathode electrode catalyst layer at a portion on the side of the cathode diffusion layer is higher than at a portion on the side of the polymer electrolyte membrane and electron conductivity of the cathode electrode catalyst layer at the portion on the side of the polymer electrolyte membrane is lower than at the portion on the side of the cathode diffusion layer, and furthermore, electron conductivity of the anode electrode catalyst layer at a portion on the side of the anode diffusion layer is higher than at a portion on the side of the polymer electrolyte membrane and electron conductivity of the anode electrode catalyst layer at the portion on the side of the polymer electrolyte membrane is lower than at the portion on the side of the anode diffusion layer.
