Model catalyst studies of active sites and metal support interactions on vanadia and vanadia-supported catalysts (1991)

摘要

We have performed a resonant photoemission study on both stoichiometric and defect TiO(sub 2) (110) surfaces using synchrotron radiation. A resonant enhancement of the O(2p) valence band photoemission intensity is observed for both nearly Perfect and reduced TiO(sub 2) surfaces as the photon energy is swept through the Ti 3p (ge) 3d optical transition energy, which indicates a strong hybridization between the O and Ti ions. Changes in the shape of the O(2p) band are also observed. As compared to the nearly perfect surface, the reduced surface has higher emission intensity from the bonding orbitals relative to the nonbonding orbitals. In addition, the intensity of emission from the O(2p) bonding orbitals resonates more than that from the O(2p) nonbonding orbitals for both nearly perfect and reduced surfaces. The resonant enhancement for the O(2p) bonding orbitals is consistent with theoretical calculations, which predict that the O(2p)-Ti(3d) hybridization involves primarily those O(2p) orbitals; the origin and energy dependence of the resonant enhancement for the O(2p) nonbonding orbitals are not understood. The spectra for the defect surface exhibit a resonant change in the intensity of the Ti(3d) emission as well, which is similar to those reported for Ti(sub 2)O(sub 3), SrTiO(sub 3-x) and Ti metal.