The catalytic effect of a SnO2 co-catalyst for ethanol electrooxidation on polycrystalline Pt is studied by electrochemical methods, in situ infrared reflection-absorption spectroscopy, and high resolution transmission electron microscopy. The electrochemical results show that deposition of small SnO2 NPs onto the pc-Pt electrode surface significantly enhances the catalytic performance of Pt. Infrared spectroscopy measurements show the effect that small SnO2 particles have on the removal of CO from the Pt surface and suggest that the electrocatalytic C-C bond splitting activity of Pt, the key step in full conversion of ethanol to CO2, is not affected by the addition of the -OH species provided by the SnO2 particles. Also, it is shown that controlled deposition of SnO2 is needed in order to,control the rate of partial oxidation to acetic acid compared to full oxidation to CO2. The combined results provide new insight into the role of SnO2 co-catalysts in promoting the electro-oxidation of ethanol to CO2 on Pt surfaces. (C) 2014 Elsevier B.V. All rights reserved.