Thermally activated redox-processes in V2O5-x under high oxygen partial pressures investigated by means of impedance spectroscopy and Rutherford backscattering

Abstract

Electrochemical methods have been applied in the catalytic system V2O5 in order to investigate the redox properties and their correlation with catalytic properties. Temperature programmed conductivity measurements using electrochemical impedance spectroscopy enabled us to determine the onset of a thermally induced reduction at about 380°C. Rutherford backscattering analysis provides evidence for a reduction from V+5 to V+4. Experiments under different oxygen partial pressures showed that the vanadyl oxygen is involved in the reduction process and it was possible to determine the energy of formation for an oxygen vacancy as 1.23 ± 0.03 eV. The removability of the vanadyl oxygen is assumed to be a key factor for the catalytic activity so that it can be characterized by macroscopic transport properties.