Carbonyl cluster compounds are promising potential substitutes for platinum as catalysts in fuel cells. In this work, we have used Ir-4(CO)(12) as a new electrocatalyst to study its activity for the Oxygen Reduction Reaction (ORR) in the absence and presence of methanol in different concentrations (1.0 and 2.0 mol L-1), and the Hydrogen Oxidation Reaction (HOR) with pure hydrogen and hydrogen/carbon monoxide mixtures ([CO] = 100 ppm and 0.5%). This iridium cluster can perform both the ORR and HOR, and it exhibits the important property of being tolerant to the aforementioned contaminants to an important extent, in contrast to platinum, which is easily deactivated even by traces of CO or methanol. The compound was electrochemically studied by rotating disk electrode (RDE) measurements, using the cyclic and linear sweep voltammetry (CV and LSV) techniques. The ORR temperature dependence (293 K-333 K) was studied and kinetic parameters such as the Tafel slope, charge transfer coefficient, exchange current density and activation energy were calculated from the LSV polarization curves. This carbonyl complex is one of the few transition metal clusters whose catalytic activity for these reactions has been reported. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.