Valence of vanadium in hydrated compounds

Problems of the definition of vanadium chemical states in the mixed valency compounds are examined. The statistical analysis of the literature data on the values of binding energy and full width at half maximum (FWHM) of V 2p(3/2) peaks in different vanadium oxides is carried out. X-ray photoelectron spectroscopy was used to determine the chemical shift and FWHM of V 2p peaks of V4+ and V5+ cations in the vanadium pentoxide matrix of hydrated vanadium compounds HV12O31 center dot nH(2)O and (VO)V12O31 center dot nH(2)O, prepared by using sot-gel technology. It was found that the binding energy of V4+ ions shifts to the lower energy side of about 1.3 eV as compared to the main V5+ ions in the matrix. The V 2P(3/2) line width for tetra-valent vanadium ions in xerogels is actually the same as for penta-valent ions.