Electrochemical study of the decorated Pt@Au catalyst synthesized by Cu underpotential deposition (UPD)-Pt redox replacement technique has been conducted in this work. The parameters affecting the Cu UPD on Au/C nanoparticles in sulfuric acid electrolyte, including the UPD potential, deposition time and potential sweep rate, were investigated in detail. Anode stripping method was used to calculate the charge of the deposited Cu adlayers. Results showed that Pt@Au catalyst prepared by this UPD-redox replacement approach is not a core-shell structure but a decorated structure. A series of decorated Pt@Au/C catalysts with various Pt coverages were synthesized and examined for formic acid oxidation (FAO). It is found that the specific activity of Pt atoms increases with the decrease of Pt surface coverage on Au. Life test showed that better stability was pertained for this decorated Pt@Au/C catalyst compared to Pt/C towards FAO. (C) 2008 Elsevier Ltd. All rights reserved.