A transition metal cluster of the type RuxFey electrocatalyst was synthesized in 1,6-hexanediol (bp approximate to 250degreesC), by reacting the transition metal carbonyl compounds RU3(CO)(12) and Fe(CO)(5) under refluxing condition for 2 h. The powder was characterized by FTIR, X-ray diffraction, Scanning electron microscope and transmission electron microscopy analysis. The average diameter of the electrocatalyst is found to be 2.5 nm. Efficient electrocatalytic activity at low overpotential for the molecular oxygen reduction in 0.5 M H2SO4 was obtained, The kinetics was investigated using Nafion(R)-coated RuxFey. cluster catalyst supporting on carbon Vulcan XC-72 rotating disk electrode. An enhancement of the electrocatalytic activity of nanoparticles of ruthenium by incorporating < 5% iron content in the ruthenium-based catalyst was observed. Kinetic studies showed a first-order reaction with a Tafel slope of -0.140 V/dcc and an exchange current density of 2.7 x 10(-5) mA cm(-2) at 298 K. (C) 2002 Published by Elsevier Science Ltd on behalf of the International Association for Hydrogen Energy.