Dynamical and structural properties of adsorbed water molecules at the TiO2 anatase-(1 0 1) surface: Importance of interfacial hydrogen-bond rearrangements

Abstract

Dynamical and structural properties of physically- and chemically-adsorbed water molecules on partially hydroxylated anatase-(1 0 1) surfaces have been studied via Born-Oppenheimer molecular dynamics. Most molecules adopt surface-parallel orientations. Two main types of water-splitting modes were: at a Ti5 site, rupturing the neighbouring oxygen-atom bridge featuring two surface OH-groups connected with a hydrogen bond, and a co-catalytic molecule in the hydration layer forming an intermediate hydronium ion donating a proton to a bridging oxygen atom. A 1155 cm−1 vibrational mode arises from ‘deformation’ in OH-groups, bound to surface-adsorbed water molecules by weak hydrogen bonds – a key ‘signature’ of covalently-shared protons.