Solvation-Induced Changes in the Mechanism of Alcohol Oxidation at Gold/Titania Nanocatalysts in the Aqueous Phase versus Gas Phase.

Gold/titania catalysts are widely used for key reactions, notably including the selective oxidation of alcohols in the liquid phase. Our large-scale ab initio simulations disclose that the liquid-phase reaction mechanism is distinctly different from that in the gas phase because of active participation of water molecules. While concerted charge transfers related to O2 splitting and abstraction of both protonic and hydridic hydrogens are enforced under dry conditions, stepwise charge transfer is preferred in the condensed phase. Dissociation of reactive water molecules and subsequent Grotthuss migration of protonic defects, H+ (aq), allows for such a decoupling of the oxidation process, both in time and space. It is expected that these observations are paradigmatic for heterogeneous catalysis in aqueous phases.