Proton exchange membrane fuel cells (PEMFCs) are promising mobile power supply systems, and operate without noise or polluting emissions. Because the oxygen reduction reaction (ORR) at the cathode suffers from high overpotential and sluggish kinetics, many catalysts have been developed in efforts to enhance activity and durability for the ORR. However, most of them have complicated synthetic procedures which cannot be scaled up easily, and have only been tested in a half-cell. High activity in a half-cell does not necessarily guarantee better performance in a single-cell. In this work, we synthesized an Au-doped PtCo/C catalyst using a simple method of gas-phase reduction and subsequent galvanic replacement, and its activity and durability were tested in a single-cell. When current densities were compared at 0.6 V after a durability test of 30,000 cycles in 0.6-1.0 V, the values were 1.40, 0.81, and 0.63 A cm(-2) for the Au-doped PtCo/C, acid-treated PtCo/C, and commercial Pt/C catalysts, respectively. Co leaching was much less in the Au-doped PtCo/C. Density functional theory (DFT) calculations confirmed that surface oxygen species bound more weakly at the catalyst surface and migration of a Co atom (Co segregation) to the surface was suppressed in the presence of Au. This facile method can provide a more realistic strategy to design better ORR catalysts for PEMFC application.