First-Principles Study of Adsorption of Dimethyl Methylphosphonate on the TiO2 Anatase (001) Surface: Formation of a Stable Titanyl (Ti=O) Site

Ab initio calculations have been performed to model the molecular adsorption of dimethyl methylphosphonate (DMMP) on the (001) surface of the anatase form of TiO2. Both the relaxed unreconstructed (1 x 1)- and the (4 x 1)reconstructed clean surfaces have been analyzed. Adsorption occurs via a Ti-O=P dative bond to a coordinatively unsaturated surface Ti site. In both cases, one of the two Ti-O-Ti bridge bonds at the Ti adsorption site breaks leading to the formation of a stable Ti=O titanyl group. This species has not been reported in previous studies of adsorption on TiO2 surfaces but is seen, in the present work, as an intermediate in the dissociative adsorption of H2O.