Thermal reduction of vanadium pentoxide: an XPD study

Transition metal oxide surfaces are of interest for a number of catalytic phenomena. In the framework of a V2O5/TiO2 catalyst project, the reduction of V2O5 to lower oxides is investigated by means of X-ray photoelectron diffraction (XPD). Cleaved V2O5(001) surfaces, previously characterized by means of XPD in combination with single scattering simulations, were now reduced by heating (500 degrees C) under an O-2 atmosphere (5 x 10(-4) Torr, 1 h). XPD intensity patterns were recorded with a laboratory XPS apparatus equipped with an Al K alpha 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 V2O5(001), oxygen deficient V2O5(001) and V6O13(001) structures. V6O13 is a shear structure of V2O5 and alternates double and single VO-layers. It is seen that the simulations for the single crystal V6O13 reproduce the experimental XPD patterns best. Moreover, the results point towards a termination of the V6O13(001) structure, where the double VO-layer is at the top. (C) 1999 Elsevier Science B.V. All rights reserved.