DFT study on the reaction mechanisms behind the catalytic oxidation of benzyl alcohol into benzaldehyde by O2 over anatase TiO2 surfaces with hydroxyl groups: Role of visible-light irradiation

Theoretical study on the catalytic oxidation of benzyl alcohol by molecular oxygen (O-2) on the TiO2 surface was performed by DFT calculations. The anatase TiO2 crystal faces in the absence and presence of surface hydroxyl groups were modeled with a slab of Ti16O32 and Ti16O32(OH)H, respectively. The interaction of benzyl alcohol with Ti16O32 and Ti16O32(OH)H was calculated. It was clearly demonstrated that the surface hydroxyl groups on the TiO2 surface play a significant role in the formation of the alkoxide [Ti]-O-CH2-ph) species. The orbitals of the alkoxide species was found to be hybridized with the O2p orbital in the valence band (VB) of the TiO2. The origin of the visible-light response in the photo catalytic system can be attributed to the electronic transition from the donor levels created by the alkoxide species to the conduction band (CB). Furthermore, reaction coordinates in the overall catalytic reaction of benzyl alcohol into benzaldehyde on the TiO2 surface were demonstrated, and the role of the visible-light irradiation was also discussed. (C) 2015 Elsevier B.V. All rights reserved.