Pathway-Switching Mechanism for Water-Catalyzed Ethanol Decomposition on Cu(111)

A first-principles study of the ethanol decomposition mechanism on Cu(111) is presented with a focus on the selectivity of acetaldehyde production controlled through the addition of molecular water in the reaction network. We include a pathway-switching bimolecular mechanism in which water and a substrate species undergo a double hydrogen exchange reaction, which alters the decomposition pathway of ethanol. The mechanistic study is performed on a portion of the ethanol decomposition network consisting of eight hydrogen abstraction reactions, adsorption of ethanol, desorption of acetaldehyde, and addition of two water-catalyzed pathway-switching reactions. The reaction rates are determined with density functional theory (DFT) and transition-state theory (TST). We use a recently developed technique, the sum over histories representation SOHR, to describe the chemical pathways of ethanol decomposition. The addition of the water pathway-switching mechanism shows an increase of acetaldehyde production, which closely follows experimental results.