This research aims to improve the activity of Pt-Ru nanoparticle electrocatalysts and thus, to lower the catalyst loading in anodes for methanol electrooxidation. The direct methanol fuel cell (DMFC) anodic Pt-Ru/C nanoparticle electrocatalysts were prepared using a chemical reduction method. The pH values of the reductive solutions were adjusted by different buffer solutions of CH3COONa-NaOH, C6H5Na3O7-NaOH, and Na2CO3-NaHCO3, respectively. The performance of the nanoparticle electrocatalysts were examined by cyclic voltammetry, chronoamperometry, and amperometric i-t curves using a glassy carbon working electrode in a solution of 0.5 mol L-1 CH3OH and 0.5 mol L-1 H2SO4. The structures and micro-morphology of the Pt-Ru/C nanoparticles were determined and observed by X-ray diffraction (XRD) and transmission electron microscopy. XRD analysis showed that all of catalysts exhibited face-centered cubic (fcc) structures. No diffraction peaks indicated the presence of either pure Ru or Ru-rich hexagonal close packed (hcp) phase. The size of the Pt-Ru/C nanoparticles prepared with a C6H5Na3O7-NaOH solution was relatively small similar to 4.3 rim. Its size distribution in carbon was more homogeneous. The electrochemical active measurements results showed that the catalytic activity and the stability of Pt-Ru/C nanoparticle electrocatalyst prepared with a C6H5Na3O7-NaOH solution for methanol electrooxidation was higher than that from the other solutions due to the citrate complexation stabilizing effect and a competing adsorption effect. (c) 2007 Elsevier B.V. All rights reserved.