Density functional theory calculations for the interaction of oxygen with reduced M/SnO2(110) (M = Pd, Pt) surfaces

Density functional theory calculations within the generalized gradient approximation have been performed for the interaction of oxygen with reduced M/SnO2(1 10) (M = Pd, Pt) surfaces. There are larger dissociation barriers of side-on type chemisorbed O-2 molecules assigned as a superoxo (O-2(-)) species for Pd/SnO2, an intermediate oxygen species between O-2(-) and preoxo (O-2(2-)) for Pt/SnO2 than the barrier less dissociation of O-2(2-) for the reduced SnO2(110) surface. 2 2 2 An adsorbed O- species produced by the dissociation of these species shows higher migration barriers of approximate to30-40 kcal/ mol over the noble metal, indicating its limited migration on the surfaces. It is also found that the catalytic activity of O- is much weakened at vacant bridging oxygen sites connected to the noble metal. These characters of O- on the surfaces may favor the selective oxidation of methane to C-1 -oxygenates (methanol and formaldehyde) compared to the SnO2 surface remaining a highly catalytically active O- under the lower migration barriers. (C) 2002 Published by Elsevier Science B.V.