Adsorption of CO2 on oxidized, defected, hydrogen and oxygen covered rutile (1x1)-TiO2(110)

Presented are initial, S-0 and coverage, Theta, dependent S(Theta), adsorption probability measurements of CO2 as a function of impact energy, E-i = 0.12-1.3 eV, adsorption temperature, T-s = 85-300 K, hydrogen and oxygen pre-exposure, as well as density of defects, G, as varied by annealing ( T = 600-900 K) and Ar+ ion sputtering (dose chi(Ar) at 600 eV at 85 K) of a rutile (1 x 1) TiO2(110) surface. The defect densities were qualitatively characterized by thermal desorption spectroscopy (TDS) of CO2. The CO2 TDS curves consisted of two structures that can be assigned to adsorption on pristine and oxygen vacancy sites, in agreement with earlier studies. S-0 decreased linearly with Ei and was independent of Ts. The adsorption dynamics were dominated by the effect of precursor states leading to Kisliuk-like shapes over the Ei and Ts range studied. Oxygen vacancy sites reduced S-0 of CO2. Preadsorbed oxygen blocked preferentially defect sites, which led to an increase in S-0. Hydrogen preadsorption results in physical site blocking with decreased S-0 as H-preexposure increased, while the shape of S(Theta) curves was conserved. In contrast to oxygen, hydrogen does not adsorb preferentially on defect sites. The adsorption probability data were parameterized by analytic functions (Kisliuk model) and by Monte Carlo simulations (MCSs).