Structure and Reactivity of Anatase TiO2(001)-(1 x 4) Surface

TiO2 anatase (001) surface which usually exhibits (1 X 4) surface reconstruction has attracted lots of research interests for its potentially high photocatalytic activity. The atomic structure of the reconstruction and defects of this surface play an important role on its reactivity. Besides the well-known add-molecule model reconstruction, the add-oxygen model (AOM) for anatase (001)-(1 X 4)-reconstructed surface by adding one oxygen atom to each Ti-4C atom was proposed. In this work, we investigate the geometric and electronic structures as well as the H2O and O-2 adsorption behavior on anatase (001) surface with AOM systematically. The different defect structures including oxygen vacancy (O-v), Ti interstitial (Ti-ini), and TiO2 vacancy (TiO2)(v) are also studied. Our calculations show that oxidization makes the AOM surface inert to molecular adsorption. The TiO2 vacancy with Ti interstitial, (TiO2)(v)-Ti-ini, is found to be the only reactive site for water and oxygen molecules adsorbing on the TiO2 anatase (001)-(1 X 4)-reconstructed surface. The investigations based on AOM can explain the atomic-resolved scanning tunneling microscopy results appropriately. Our systematic study of the AOM reconstruction of anatase (001) provides new insights into the understanding of the structure and reactivity on this surface.