The influence of the structure and morphology of PtRu nanoparticles supported on functionalized carbon black has been investigated for CO and methanol electrooxidation in a half-cell and in a DMFC single cell. Carbon black was treated with HNO3 to obtain an oxidized surface (Vulcan-N), and PtRu nanoparticles supported on Vulcan-N were prepared via impregnation, Bonnemann's method and the sulfito-complex route. Temperature programmed reduction (TPR) measurements evidence the presence of RuO2 center dot xH(2)O phase in the catalyst obtained by the sulfito-complex route. This phase was stabilized by metal-support interaction, whereas alloy characteristics were estimated for PtRu catalyst obtained by impregnation and Bonnemann's method. The nature of the precursor-support interaction, induced by the nature of the functional groups on the carbon surface, affects the structure of the electrocatalyst and subsequent behavior in electroactivity. When synthesized through Bonnemann's method, the surface oxygen-containing groups of the support seem to be unable to stabilize the anhydrous precursors of platinum and ruthenium, yielding crystalline RuO2. Methanol electrooxidation performance was clearly different in the three catalysts, whereas only a few negligible differences were observed in CO oxidation. The superior performance in DMFC of the catalysts obtained by the sulfito-complex route accounts for both the presence of RuO2 center dot xH(2)O species and the functionalization of carbon black. (C) 2008 Elsevier B.V. All rights reserved.