The direct formic acid fuel cell (DFAFC) has two major shortcomings that limit its lifespan and performance: (i) the poor electrocatalytic stability of the carbon supported Pd (Pd/C) catalyst and (ii) rapid decomposition of formic acid over the Pd/C catalyst. To solve the problems, the carbon-supported Pd-Cu (Pd-Cu/C) catalysts with different atomic ratios of Pd and Cu are successfully prepared with a simple impregnation-reduction method. It is reported for the first time that the electrocatalytic performances of the Pd-Cu/C catalysts for formic acid oxidation are related to the decomposition rate of formic acid over the Pd-Cu/C catalysts. When the content of Cu in the Pd-Cu/C catalysts is gradually increased, the decomposition rate of formic acid over the Pd-Cu/C catalysts is correspondingly decreased, leading to the decrease in the production of poisoned CO. Therefore, the electrocatalytic performances of the Pd-Cu/C catalysts for formic acid oxidation are much better than that of the Pd/C catalyst. However, when the content of Cu in the Pd-Cu/C catalyst is too high, the electrocatalytic performance of the Pd-Cu/C catalyst would be decreased because Cu has no electrocatalytic activity for formic acid oxidation. Based on the above reasons, among all Pd-Cu/C catalysts prepared, the electrocatalytic performance of the Pd-Cu/C catalyst with 3:1 atomic ratio of Pd and Cu for formic acid oxidation is best. (C) 2012 Published by Elsevier Ltd.