Controlling the morphology and composition of Pt-based catalysts can enhance their catalytic properties. We synthesize different Pt-Au alloy catalysts by electrodeposition in variable precursor solutions containing H2PtCl6 and HAuCl4. The Pt-Au catalysts are characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical methods. We find that Pt-Au alloys are formed and the atomic ratios of Pt/Au in the alloys are close to the concentration ratio of H2PtCl6/HAuCl4 in the precursor solutions. The presence of Au in the Pt-Au alloys change the pathway of formic acid oxidation (FAO) reaction, and the Pt-Au alloy catalysts have higher catalytic activity than that of pure Pt catalyst. When the ratio of H2PtCl6/HAuCl4 is 3:1, the Pt3Au1 alloy possesses the highest catalytic activity for the formic acid oxidation, which is nearly four times more active than that of the pure Pt catalyst. (C) 2013 The Electrochemical Society. All rights reserved.