Enhancement in Ethanol Electrooxidation by SnOx Nanoislands Grown on Pt(111): Effect of Metal Oxide-Metal Interface Sites

An integrated surface science and electrochemistry approach has been used to prepare and characterize SnOx/Pt(111) model catalysts and evaluate their electrochemical activity for the ethanol oxidation reaction (EOR). Nanoislands of SnOx are deposited onto the Pt(111) by reactive layer assisted deposition in which Sn metal is vapor deposited onto a Pt(111) surface precovered by NO2. X-ray photoelectron spectroscopy (XPS) shows that the SnOx islands are highly reduced with Sn2+ being the dominant chemical species. After exposing the SnOx/Pt(111) surface to H2O or an electrolyte solution, XPS provides evidence for a significant amount of H2O/OH adsorbed on the reduced SnOx surfaces. Electrochemical testing reveals that the catalytic performance of Pt(111) toward ethanol electrooxidation is significantly enhanced with SnOx islands added onto the surface. The enhanced EOR activity is tentatively attributed to the efficient removal of COads-like poisoning species at Pt sites by oxygen-containing species that are readily formed on the SnOx nanoislands. Moreover, the strong dependence of the EOR activity on SnOx coverage provides experimental evidence for the importance of SnOx-Pt interface sites in the EOR.