In situ XAFS measurements were conducted in the fluorescence mode using a home-made electrochemical cell. The VO-TiO2, Ag/AgCl and graphite rod were used as working electrode, reference electrode and counter electrode, respectively. Relevant measurements were conducted in 0.1 M H2SO4 electrolyte. The XANES spectra were recorded at OCP and different applied potentials. The absorption energy (E0) is obtained from the first maximum in the first-order derivative as the electronic vacancy.