Photocatalytic reduction of oxygen molecules at the (100) TiO2 anatase surface

The adsorption, photoreduction and chemical activity of oxygen molecules on the (100) anatase surface have been investigated here together with the effects that surface oxygen vacancies (V-O) can have on these O-2-related processes. We use an original approach by treating molecules on the TiO2 surface like surface defects in the same framework successfully used for defects in semiconductors. The achieved results: (i) give the first theoretical evidence of an acceptor behaviour of an adsorbed O-2 molecule, which is at the origin of its photoreduction; (ii) show that the V-O donor character is strongly affected by the interaction with O-2; and (iii) suggest that the release of O-2(-1) radicals as well as the formation Of O-2-related radicals may be favoured by photogenerated electrons in presence of surface V-O's. (C) 2005 Elsevier B.V. All rights reserved.