Structure and Dynamics of CO2 on Rutile TiO2(110)-1×1

Abstract

Adsorption, binding, and diffusion of CO2 molecules on model rutile TiO2(110)-1×1 surfaces were investigated experimentally using scanning tunneling microscopy, infrared reflection adsorption spectroscopy (IRAS), molecular beam scattering, and temperature programmed desorption and theoretically via dispersion corrected density functional theory and ab initio molecular dynamics. In accord with previous studies, bridging oxygen (Ob) vacancies (VO’s) are found to be the most stable binding sites. Additional CO2 adsorbs on 5-coordinated Ti sites (Ti5c) with the initial small fraction stabilized by CO2 adsorbed on VO sites. The Ti5c-bound CO2 is found to be highly mobile at 50 K at coverages of up to 1/2 monolayer (ML). Theoretical studies show that the CO2 diffusion on Ti5c rows proceeds via a rotation-tumbling mechanism with extremely low barrier of 0.06 eV. The Ti5c-bound CO2 molecules are found to bind preferentially to a single Ti5c with the O═C═O axis tilted away from the surface normal. The binding ener...