NO adsorption and diffusion on hydroxylated rutile TiO2(110)

Abstract

We report a computational study of NO adsorption and diffusion on the hydroxylated rutile TiO₂(110) surface performed with density functional theory (DFT) calculations corrected by on-site Coulomb corrections and long-range dispersion interactions. NO prefers to adsorb with its N-end down at surface Ti_5c sites. The excess electron that is located at a subsurface site for the hydroxylated surface localizes in the 2π* orbital of the adsorbed NO. A novel ‘roll-over’ diffusion scheme is proposed that involves three neighboring Ti_5c atoms and one surface hydroxyl, with an O-end down NO at the middle Ti_5c as the intermediate state. During the migration, NO can also form bridging species between two Ti_5c atoms. The calculated scanning tunneling microscopy (STM) features with the “bright-dark-bright” configuration corresponding to diffusing NO at different positions are consistent with the experimental STM results.