Alloyed PdmAu nanoparticles (m refers to the atomic Pd/Au ratio), prepared through the co-reduction of K2PdCl4 and HAuCl4 precursors in aqueous solutions, are employed as the catalysts for ethanol electro-oxidation reaction (EOR) in alkaline electrolyte. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) are used to characterize the morphology and confirm the alloy structure of the samples. Cyclic voltammetry (CV) and chronoamperometry (CA) results indicate that the addition of Au to Pd can significantly improve the catalytic activity of Pd toward EOR and the improvement is strongly dependent on the composition of the catalysts. Pd1.0Au/C is identified as the most efficient catalyst since it produces the highest catalytic activity and long-term stability. The mass-specific activity (MSA) and intrinsic activity (IA) data of Pd1.0Au/C is 1.45 mA mu g(Pd+Au)(-1) and 80.2 A m(pd)(-2), which is found to be 23 and 11.3 times that of the Pd/C catalyst, respectively. These findings clearly suggest that the proximity and relative amount of Au and Pd on the surface of the nanoparticles (NPs) are crucial for the improvement of Pd catalysis, which would have important implications for designed preparation of bimetallic catalysts for the direct alcohol fuel cells. (C) 2013 Elsevier B.V. All rights reserved.