Adsorption of water on single-walled TiO2 nanotube: A DFT investigation

We have performed a density functional theory (DFT) study based on the periodic method to provide a detailed description of the electronic and adsorption properties of single-walled TiO2 anatase nanotubes. Both (n, 0) and (m, 0) TiO2 nanotubes, with diameters ranging from 9.8 إ to 23 إ, are considered for the study of structure and adsorption processes. Our calculated results show that the molecular and dissociative adsorptions of water on TiO2 nanotubes are exothermic. However, molecular adsorption is energetically favorable. Molecular adsorption of the outer surface of (n, 0) tube is energetically favorable and molecular adsorption of the inner surface of (0, m) tube is energetically favorable. Furthermore, we found that the surface curvature of TiO2NTs plays a major role in water splitting and a minor role in the molecular adsorption of water on the surface of the tubes. These results are interpreted in terms of the peculiar electronic properties of the TiO2 nanotube during the examination of the interaction among water molecules on the TiO2 nanotubes surface.