Methanol electrooxidation was investigated on the carbon-supported PtRu electrocatalyst (1:1 atomic ratio) in acid media. X-ray diffraction measurement indicated alloying of Pt and Ru. Cyclic voltammetry of the sample reflects the amount of Ruin the catalyst and its ability to adsorb OH radicals. Tafel plots for the oxidation of 0.02-3 M methanol in the solutions containing 0.05-1 M HClO4 and in the temperature range 27-40 degreesC showed reasonably well-defined linear region with the slope of about 115 mV dec(-1) at the low currents, irrespective of the experimental conditions employed. Reaction order with respect to methanol was found to be 0.5. A correlation between methanol oxidation rate and pseudocapacitive current of OH adsorption on Ru sites was established. It was proposed that bifunctional mechanism is operative with the reaction between methanol residues adsorbed on Pt sites and OH radicals adsorbed on Ru sites as the rate-determining step. (C) 2003 Elsevier Ltd. All rights reserved.