Water Adsorption and Dissociation on BaTiO3 Single-Crystal Surfaces

Experimental and theoretical studies of water-molecule adsorption on BaTiO3 single-crystal surfaces are presented in this paper. The Fourier transform infrared spectrum shows that there are three types of energy-nonequivalent active modes for water-molecule adsorption on the in-plane-polarized BaTiO3(100) surface. The X-ray photoelectron spectroscopic results illustrate hydroxyl group on the surface, thereby indicating that the adsorbed water molecules are dissociated. The first-principles calculations of the 1/4-, 1/2-, and 1-monolayer water coverage demonstrate that H bonds are formed between the hydrogen of water and the surface oxygen of BaTiO3 and between the hydrogen of hydroxyl and the surface oxygen of BaTiO3, and the difference in the water adsorption behavior on the BaO- and TiO2-terminated surfaces. The calculation results are in good agreement with the experimental observations.