Present paper reports kinetics of electro-oxidation of ethanol (EtOH) and ethylene glycol (EG) onto Pt and PtRu nanocatalysts of different compositions in the temperature range of 298-318 K. These catalysts have been characterized by SEM, EDX, XRD, CV and amperometry. It has been observed that apparent activation energies for oxidation of EtOH and EG pass through a minimum at about 15-20 at.% of Ru in the PtRu alloy catalysts. Anodic peak current vs. composition curve also shows a maximum around this composition. The results have been explained by a geometric model, which proposes requirement of an ensemble of three Pt atoms with an adjacent Ru atom onto PtRu surface for an efficient electro-oxidation of EtOH or EG. This is further supported from statistical data analysis of probability of occurrence of such ensembles onto PtRu alloy surface. Present results also suggest that electro-oxidation of EG onto nano-PtRu catalyst surfaces follows a different path from that of EtOH at alloy composition less than 15 at.% of Ru. (C) 2009 Elsevier Ltd. All rights reserved.