Well-dispersed PtRu/C catalysts were prepared by supporting surfactant-stabilized PtRu hydrosol on carbon followed by a heat-treatment at elevated temperature. The effect of the synthesis conditions and the heat-treatment on the composition and electrcatalytic properties of PtRu/C towards methanol oxidation was systematically investigated. It was found that the pH environment and the reaction temperature could greatly affect the final compositions of Pt and Ru in the PtRu catalysts. Moreover, after a post-heat-treatment process, the electrocatalytic activity of PtRu colloidal catalysts can be much improved, the enhancement of which can be largely explained by the improved alloying formation and the removal of surfactant from catalyst demonstrated by the XRD and XPS analyses, respectively. (c) 2006 Elsevier Ltd. All rights reserved.