Chemistry of O- and H-containing species on the (001) surface of anatase TiO2: a DFT study.

The chemistry of oxygen, hydrogen, water, and other species containing both oxygen and hydrogen atoms on the anatase TiO(2) (001) surface is investigated by DFT. The adsorption energy of atoms and radicals depends appreciably on the position and mode of adsorption, and on the coverage. Molecular hydrogen and oxygen interact weakly with the clean surface. However, H(2)O dissociates spontaneously to give two nonidentical hydroxyl groups, and this provides a model for hydroxylation of TiO(2) surfaces by water. The mobility of the hydroxyl groups created by water splitting is initially impeded by a diffusion barrier close to 1 eV. The O(2) adsorption energy increases significantly in the presence of H atoms. Hydroperoxy (OOH) formation is feasible if at least two H atoms are present in the direct vicinity of O(2). In the adsorbed OOH, the O-O bond is considerably lengthened and thus weakened.