Low temperature adsorption of oxygen on reduced V2O3(0001) surfaces

Well ordered V2O3(0 0 0 1) films were prepared on Au(1 1 1) and W(1 1 0) substrates. These films are terminated by a layer of vanadyl groups under typical UHV conditions. Reduction by electron bombardment may remove the oxygen atoms of the vanadyl layer, leading to a surface terminated by vanadium atoms. The interaction of oxygen with the reduced V2O3(0 0 0 1) surface has been studied in the temperature range from 80 to 6 10 K. Thermal desorption spectroscopy (TDS), infrared reflection absorption spectroscopy (IRAS), high resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) were used to study the adsorbed oxygen species. Low temperature adsorption of oxygen on reduced V2O3(0 0 0 1) occurs both dissociatively and molecularly. At 90 K a negatively charged molecular oxygen species is observed. Upon annealing the adsorbed oxygen species dissociates, re-oxidizing the reduced surface by the formation of vanadyl species. Density functional theory was employed to calculate the structure and the vibrational frequencies of the O-2 species on the surface. Using both cluster and periodic models, the surface species could be identified as eta(2)-peoxo (O-2(2-)) lying flat on surface, bonded to the surface vanadium atoms. Although the O-O vibrational normal mode involves motions almost parallel to the Surface, it can be detected by infrared spectroscopy because it is connected with a change of the dipole moment perpendicular to the surface. (c) 2006 Elsevier B.V. All rights reserved.