Ethanol is a renewable fuel that can be used as an additive to gasoline (or its substitute) with the advantage of octane enhancement and reduced carbon monoxide exhaust emissions. However, on the standard three-way catalysts, the conversion of unburned ethanol is low because both ethanol and some of its partially oxidized derivatives are highly resistant to oxidation. A combination of first-principles density-functional theory (DFT)-based calculations and in situ diffuse reflectance infrared spectroscopy (DRIFTS) analysis was applied to uncover some of the fundamental phenomena associated with ethanol oxidation on Pt-containing catalysts. In particular, the objective was to analyze the role of the oxide (i.e., gamma-Al(2)O(3) or SiO(2)) substrate on the ethanol oxidation activity. The results suggest that Pt nanoparticles trap and accumulate oxygen at their surface and perimeter sites and play the role of sites that burn ethanol molecules and their partially oxidized derivatives to the final products. The gamma-Al(2)O(3) surfaces provided higher mobility of the fragments of ethanol molecules than the SiO(2) surface and hence increased the supply rate of these species to the Pt particles. This in turn produces a higher conversion rate of unburned ethanol. (C) 2009 Elsevier B.V. All rights reserved.