Ethanol is a renewable fuel that can be used as an additive to gasoline 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 acetaldehyde are highly resistant to oxidation. In this work we use a combination of in-situ diffuse reflectance infrared spectroscopy (DRIFTS) analysis and first-principles density-functional calculations to uncover the fundamental phenomena associated with ethanol oxidation on Pt containing catalysts. We show that Pt particles accumulate oxygen at their surface and play the key role in burning ethanol molecules and their fragments. The oxide surfaces at which the mobility of molecular fragments is high provide the highest supply rate of these objects to the Pt particles (and the highest oxidation rate). These results explain the differences in ethanol oxidation process on the Pt-on-silica and Pt-on-alumina catalysts.