A theoretical study of CO2 adsorption on TiO2

This paper presents a theoretical study of the interaction of CO2 with the rutile TiO2 surface. The calculations are performed using the periodic Hartree-Fock CRYSTAL program. Several modes for the adsorption are investigated. On the bare surface at theta = 1/2, the best adsorption mode is obtained when the CO2 molecule is vertically adsorbed over a titanium atom; at saturation, the CO2 molecules are tilted toward the surface; then, the adsorption mode is also controlled by the adsorbate-adsorbate interactions. Another adsorption mode, competitive with the first one, corresponds to a parallel CO2 molecule over two titanium atoms. The adsorption over an oxygen atom of the oxide is weak. On the hydrated surface, the presence of hydroxyl groups favors the CO2 adsorption and leads to the formation of adsorbed bicarbonate ions.