Electronic interactions in the vanadium/TiO2(110) and vanadia/TiO2(110) model catalyst systems

Abstract

We have studied model catalysts comprised of vanadium or vanadia deposited onto both stoichiometric and reduced single-crystal TiO2(110) surfaces by using XPS, UPS, Auger, LEED and work-function measurements. Changes in the electronic and geometric structure of TiO2 supports are monitored during overlayer formation in the submonolayer and monolayer regimes. Deposition of vanadium in an O2 ambient onto the stoichiometric TiO2 surface results in the formation of lower oxides of vanadium that interact only weakly with the support. However, the stoichiometric TiO2 surface is attacked violently by vanadium metal atoms deposited in UHV; in the submonolayer range, V-O bonding results in electron transfer to the substrate due to the strong affinity between V and O. This substrate reduction is confirmed by the appearance of Ti3+ features in XPS spectra. For greater than monolayer coverage, a metallic overlayer is formed. In both the vanadia/TiO2 and V/TiO2 systems, the initially sharp (1 × 1) LEED patterns disappear for small coverages, indicating disordering of the surfaces. Although defects on TiO2 are generally active chemisorption sites, the reduced TiO2 surface interacts only weakly with metallic vanadium.

Keywords

Affiliated Institutions

• Yale University US

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