First-principles study of the interaction of oxygen with the SnO2(110) surface

First-principles calculations based on density functional theory in the gen eralised gradient approximation, together with pseudopotentials and plane-w ave basis sets, have been used to investigate the energetics of oxygen adso rption on stoichiometric and weakly and strongly reduced SnO2(1 1 0) surfac es. It is shown that, if the surface species formed by oxygen adsorption ar e restricted to be charge neutral, then oxygen cannot be exothermically ads orbed from the gas phase on the stoichiometric surface. A variety of molecu lar and dissociative modes of adsorption are examined on the reduced surfac e produced by removing all bridging oxygens and on the weakly reduced surfa ce that results from removal of only a fraction of these oxygens, with the adsorbed species being in both the singlet and the triplet states, and we i dentify a number of modes not discussed before in the literature. We use th e calculated adsorption energies to propose a tentative assignment of these adsorption modes to the peaks observed in temperature programmed desorptio n experiments on the SnO2 and TiO2(1 1 0) surfaces. (C) 2001 Elsevier Scien ce B.V. All rights reserved.