Methanol and Water Dissociation on TiO2 (110): The Role of Surface Oxygen

Dissociation mechanisms for methanol and water on stoichiometric and defective TiO 2 (110) surfaces have been clarified from periodic density functional calculations. When the molecules are adsorbed on an oxygen vacancy, the most favorable route to dissociation is an indirect mechanism involving, initially, the formation of an intermediate hydroxyl group on in-plane oxygen, followed by the hydrogen transfer to a neighbor bridging oxygen. Since the transient species lifetime is short, they are difficult to be detected. At variance, dissociation on stoichiometric surfaces proceeds readily through a direct hydrogen transfer process from the adsorbate to bridging oxygen. However, the energy barrier for the recombination is low and the species can return to the initial state.