Insight into the solvent effects on ethanol oxidation on Ir(100)

Solvent effects have always been a non-negligible factor for aqueous catalytic reactions, though few studies have been devoted towards the molecular understanding and impact of solvent effects on catalysis. In this work, we investigated ethanol dehydrogenation and C-C bond cleavage over Ir(100) in an aqueous solution using density functional theory calculations with both the implicit and explicit solvent models and transition state theory-based kinetics simulations. The results show that solvent polarization assists the α- and β-dehydrogenation of ethanol on Ir(100) in the aqueous solution and hydrogen bonding also assists the ethanol β-dehydrogenation and C-C bond cleavage in CH₂CO. The hydrogen bond between the ethanol and water molecule hinders ethanol hydroxyl dehydrogenation while the CHCO⋯H2O hydrogen bond radically alters the adsorption configuration of CHCO, which leads to an increase in the C-C cleavage barrier by 2.5 fold. Furthermore, the solvent changes the reaction pathways significantly. In an aqueous solution, ethanol β-dehydrogenation on Ir(100) is the dominant ethanol dehydrogenation pathway and C-C bond cleavage occurs predominantly via CH₂CO species.