Structure and Properties of Water on the Anatase TiO2(101) Surface: From Single-Molecule Adsorption to Interface Formation

The interaction of water with titanium dioxide surfaces has a vital role in many energy- and environment-related applications, such as dye-sensitized solar cell, photocatalytic or photoelectrochemical hydrogen production, and environmental purification. Structure and properties of water on the anatase TiO2(101) surface have been studied by using a combination of density functional theory and force field molecular dynamics. Owing to the amphotericity of this surface and the competition between water water and water substrate interactions, the structure and properties of water on the anatase TiO2(101) surface exhibited some peculiar and complicated features. The overall evolutionary process of interface formation has been obtained by investigating the TiO2 adsorption configuration and energy of water. The competition between water water and water substrate interaction results in the existence of a stable bilayer of water (Theta >= 2 ML) and an ice-like structure of water at higher coverage (Theta >= 3 ML). Both static and dynamic calculation results have showed that a highly ordered structure occurs in the first few water molecule layers, and this order decreases as one moves toward the bulk region. The electric fields across the interface and in the electric double layer were estimated to be about 10 and 2 eV, respectively. This study may provide new insight into the static and dynamic properties of the water-TiO2 interface and elucidate the reactions that occur on the TiO2 surface.