The pulse electro-deposition processes created the PtCo alloy catalysts directly on the surface of gas diffusion layer (GDL). The PtCo alloy catalysts was well dispersed in GDL. By increasing cobalt contents, the size of PtCo alloy catalysts was decreased, result in the enhancement of ESA. Enhanced performance and durability of platinum might be due to the both of structural change and decrease of particle size of platinum.