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.