Computational investigation of the adsorption and photocleavage of chlorobenzene on anatase TiO 2 surfaces

Abstract

The adsorption and photocleavage of chlorobenzene (CB) molecule on the anatase TiO 2 (0 0 1), (1 0 0) and (0 1 0) surfaces are studied with semiempirical SCF MO method, MSINDO. The surfaces have been modeled with two saturated clusters Ti 21O 58H 32 and Ti 36O 90H 36. The dissociative perpendicular adsorption of CB on TiO 2 (0 1 0) and (1 0 0) surfaces revealed comparable stabilities and much higher than on the (0 0 1) surface. The aromatic ring cleavage by atomic oxygen, singlet oxygen and superoxide anion molecules has been investigated computationally and relevant mechanisms are proposed. Molecular dynamics (MD) simulations have been implemented for the adsorption models and the early stages of photocleavage mechanisms. The oxygen-type chemistry is involved actively in the water mediated photocleavage step upon excitation. The O 2 - radical anion dependant ring opening mechanism, through the dioxetane intermediate, is thermodynamically the most favourable.