Adsorption and interaction of CO2 on rutile TiO2(110) surfaces: a combined UHV-FTIRS and theoretical simulation study

Abstract

CO₂ adsorption and interaction on rutile TiO₂(110) surfaces was studied by UHV-FTIRS combined with theoretical simulations. With increasing CO₂ exposure, CO₂ adsorbs in succession at the oxygen vacancy (Vo) sites, on the five-coordinated Ti cation (Ti_5c) sites and the bridging oxygen (O_br) sites at low temperature. The coupling has occurred between neighboring CO₂ adsorbed on Ti_5c sites from rather low CO₂ coverage (∼0.5 ML), leading the ν₃(OCO) asymmetric stretching vibrations to split into two absorption bands in IR spectra. Two kinds of coupled geometries of adjacent CO₂ on Ti_5c sites are determined by theoretical simulations. For the higher CO₂ coverage (∼1.5 ML), the horizontal adsorption configuration along the [10] azimuth of CO₂ adsorbed on O_br sites is identified for the first time using polarization- and azimuth-resolved RAIRS in experiments. The significant deviation of CO₂ from the top of O_br sites demonstrates the strong coupling between CO₂ adsorbed on O_br and Ti_5c sites.