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 OCO 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.

Adsorption of ethanol on ZnO powder was studied by infrared spectroscopy followed by computational investigations. Multiple reaction cycles and various thermal regimes allowed us to identify the main bidentate ligand and compare it to the surface species produced by acetaldehyde and acetic acid dosed onto the same ZnO powder.Figure optionsDownload high-quality image (170 K)Download as PowerPoint slideHighlights
► We investigate thermal transformations of ethanol on ZnO powder.
► We use infrared spectroscopy and computational calculations for analysis.
► We design computational cluster models to describe most common surface sites.
► We investigate the changes on a surface in the course of reaction.
► We explain the spectroscopic signature of the observed species.