Methanol oxidation on carbon-supported Pt-Ru-Ni ternary alloy nanoparticles was investigated based on the porous thin-film electrode technique and compared with that on Johnson-Matthey Pt-Ru alloy catalyst. Emphasis is placed on the effect of alloying degree on the electrocatalytic activity and stability of the ternary catalysts. The as-prepared Pt-Ru-Ni nanoparticles exhibited a single phase fcc disordered structure, and a typical TEM image indicates that the mean diameter is ca. 2.2 nm, with a narrow particle size distribution. Also, the as prepared Pt-Ru-Ni catalysts exhibited significantly enhanced electrocatalytic activity and good stability for methanol oxidation in comparison to commercial Pt-Ru catalyst available from Johnson-Matthey. The highest activity of methanol oxidation on Pt-Ru-Ni catalysts was found with a Pt-Ru-Ni atomic ratio of 60:30: 10 and at a heat-treatment temperature of ca. 175 degrees C. The significantly enhanced catalytic activity for methanol oxidation is attributed to the high dispersion of the ternary catalyst, to the role of Ni as a promotion agent, and especially to the presence of hydroxyl Ru oxide. Moreover, the stability of the ternary nanocatalytic system was found to be greatly improved at heat-treatment temperatures higher than ca. 250 degrees C, likely due to a higher alloying degree at such temperatures for the ternary catalysts. (c) 2007 Elsevier B.V. All rights reserved.