Thermal reduction of vanadium pentoxide: an XPD study

Abstract

Transition metal oxide surfaces are of interest for a number of catalytic phenomena. In the framework of a V 2O 5/TiO 2 catalyst project, the reduction of V 2O 5 to lower oxides is investigated by means of X-ray photoelectron diffraction (XPD). Cleaved V 2O 5(001) surfaces, previously characterized by means of XPD in combination with single scattering simulations, were now reduced by heating (500°C) under an O 2 atmosphere (5×10 −4 Torr, 1 h). XPD intensity patterns were recorded with a laboratory XPS apparatus equipped with an Al Kα source (V 2p 3/2, E k=960 eV), as well as at the LURE synchrotron radiation facility (V 3p 3/2, E k=68 eV). Single scattering simulations were performed for V 2O 5(001), oxygen deficient V 2O 5(001) and V 6O 13(001) structures. V 6O 13 is a shear structure of V 2O 5 and alternates double and single VO-layers. It is seen that the simulations for the single crystal V 6O 13 reproduce the experimental XPD patterns best. Moreover, the results point towards a termination of the V 6O 13(001) structure, where the double VO-layer is at the top.