Single Water Molecule Adsorption and Decomposition on the Low-Index Stoichiometric Rutile TiO2 Surfaces

The adsorption behavior and decomposition process of a single water molecule on the low-index rutile TiO2 surfaces, including (110), (100), and (001), were systematically investigated by using density functional theory calculations. For both molecular and dissociative adsorption, the adsorption energy on these low-index surfaces increases in the order (110) < (100) < (001), while the activation energy of water partial decomposition reaction increases in the order (100) < (110) < (001). In the case of water adsorption on (001) surface, due to its rather flat surface and the stronger interaction with water molecule or its decomposition products, the adsorption energy for water molecule or its decomposition products is the largest; the activation energy of water decomposition on (001) surface is the smallest; and the final decomposition is two surface-adsorbed hydroxyl radicals. Therefore, the photocatalytic water splitting or photocatalytic reaction on rutile (001) surface is more easily accomplished than that of the other two surfaces. The findings in this Article are consistent with experimental observations in published literature, and will be helpful for future development of efficient photocatalysts.