A platinum overlayer was prepared on An nanoparticles that were electrodeposited on a graphite electrode by replacement of the under-potential deposition (UPD) Cu monolayer. The micrographs and element composition of Au nanoparticles and UPD Cu monolayers were characterized by scanning electron microscopy (SEM) and energy disperse X-ray spectroscopy (EDS), respectively. The electrocatalytic properties of Pt overlayer/Au/graphite electrode for methanol oxidation have been investigated by cyclic voltammetry (CV). High electroactivity and good long-term stability can be observed. These results indicate that the core (Au nanoparticle)-shell (Pt overlayer) nanocatalyst obtained by the above method may have good potential applications in designing noble metal catalysts with super low loading and high activity at the atomic level in fuel cells. (C) 2004 Elsevier B.V. All rights reserved.