In this study, Co-modified Pt/C catalysts were prepared by chemical vapor deposition (CVD) of Co on Pt/C. The performance of these catalysts as a cathode in proton exchange membrane fuel cells (PEMFCs), evaluated by a half-cell test, was compared with that of catalysts prepared using the conventional impregnation (IMP) method. The activity of the catalysts for oxygen reduction reaction (ORR) changed showing a maximum with the amounts of added Co and temperatures used for annealing the catalysts. The amount of Co needed to produce the maximum activity was smaller for the catalysts prepared by CVD ((CO/Pt)(CVD) = 0.2) than those prepared using the IMP method ((Co/Pt)(IMP) = 1.0). Furthermore, the maximum activity of the catalysts prepared by CVD was 1.5 times higher than for the catalysts prepared by IMP. The ORR activity of the IMP catalyst was degraded by 65% after the corrosion test for 6000 s, which was largely attributed to Co dissolution in the acidic solution, whereas the CVD catalyst showed only 36% degradation. The higher corrosion resistance of the CVD catalyst was attributed to the more intimate Co interactions with the Pt surface than in the catalyst produced using the IMP method. (c) 2006 Elsevier B.V. All rights reserved.