Methanol electro-oxidation on Pt-modified An nanoparticles was studied in aqueous 0.5 M H2SO4/(1) M CH3OH. The Pt-modified An nanoparticles showed lower values than pure Pt nanoparticles in area-specific current densities. The activity also decreased with lower amounts of Pt on the Pt-modified Au nanoparticles. This result indicates that the intrinsic activities of the Pt-modified Au nanoparticles were lower than that of Pt/C. This phenomenon may be due to the strengthened Pt-CO bonding or the weakened ensemble effect in the methanol electro-oxidation. However, in the Pt-specific current densities, the Pt-modified An nanoparticles showed higher values than pure Pt nanoparticles. This enhanced electrocatalytic activity could be attributed to more reaction-favorable surface structures of Pt-modified Au nanoparticles, which most likely lead a high level of Pt utilization for the electro-oxidation reaction. (C) 2007 Elsevier B.V All fights reserved.