Surface species formed during thermal transformation of ethanol on ZnO powder

Adsorption of ethanol on ZnO powder was studied by infrared spectroscopy and density functional theory investigations. With most previous investigations of ethanol conversion over ZnO focused on thermal chemistry followed by thermal desorption, some of the key questions related to the adsorbed species and the mechanism of their conversion into products still remain unanswered. It is especially important for the realistic catalytic conditions, where elevated surface temperature, availability of various surface adatoms, and defects make the mechanistic studies challenging. We find that the initial dissociative adsorption resulting in a monodentate surface ethoxy intermediate characterized by clear CH3 deformational modes at 1386 cm−1, is immediately followed by the formation of a bidentate ligand with a characteristic Osingle bondCsingle bondO bridge vibration at 1560 cm−1. The mechanism of this reaction is affected substantially by the presence of adatoms produced by preceding reactions, as was confirmed by multiple reaction cycles and supported by computational studies.