OXYGEN REACTIVITY IN VANADIUM PENTOXIDE - ELECTRONIC-STRUCTURE AND INFRARED-SPECTROSCOPY STUDIES

The activity of V2O5-lattice oxygen in oxidation reactions has been studied by a semiempirical self-consistent-field Hartree-Fock crystal orbital formalism and by infrared spectroscopy. The electronic structure of oxygen vacancies in V2O5 supports the conclusion that the most stable vacancy corresponds to the oxygen site which has the highest coordination to V atoms. Charge reorganization in the V2O5 lattice upon oxygen vacancy formation shows the tendency of the V atoms around the vacancy to accumulate electronic charge, i.e., to be reduced. The stability associated with different oxygen vacancies is related to the degree of reduction of the transition-metal atoms. The participation of lattice oxygen in V2O5 in the oxidation of dimethyl sulfoxide has been studied by infrared spectroscopy. The results of the infrared study agree with the electronic structure calculations in the sense that the oxygen atoms which participate more readily in the oxidation process correspond to those O centers with the highest V coordination. Both numerical and experimental results do not support the assumption often stressed in the literature concerning the important role of the vanadyl oxygen vacancy for the electrical and catalytic behavior of V2O5.