Physical properties of vanadium pentoxide based compounds are strongly affected by the presence of vanadium ions of reduced valence. Thus, the identification of V⁴⁺ ions in mixed valence compounds and the determination of the reduction ratio RR=V⁴⁺/(V⁵⁺+V⁴⁺) is an actual task.
Quantitative information of the relative amount of element species may be obtained from XPS data. The knowledge of BE and FWHM for individual species is required for the accurate deconvolution of the experimental spectra. Unfortunately, the known values of BE and FWHM show large discrepancy and cannot be directly used in fitting procedure.
The aim of this work is to study the main XPS peak parameters (such as BE and FWHM) of the minor V⁴⁺ ions diluted in the host V₂O₅ matrix. For this purpose the XPS spectra of the samples with different V⁴⁺ ions concentrations and the identical crystal structure were analyzed. In this case, the crystal field is the same for various valence ions, and only the vanadium ions charge affect on the chemical shift and FWHM.
Polyvanadium acid xerogel - H₂V₁₂O₃₁^.nH₂O was used as a reference material. The spectra differentiation technique indicate that the replacing of (H₂)²⁺ by a (VO)²⁺ cations allows to increase the RR of about 7%. Additional annealing of (VO)V₁₂O₃₁^.nH₂O xerogel increases the of reduced valence V⁴⁺ - ions concentration The spectra comparison technique was used to determine chemical shift and FWHM of V⁴⁺ cations in the vanadium pentoxide matrix. It was found that binding energy of V⁴⁺ ions shifts to the lover energy side of about 1.3 eV in respect to the main V⁵⁺ ions in the host matrix, while for pure main valence VO₂ and V₂O₅ this difference is about 0.6 eV. FWHM in V₂O₅ based compound is actually the same for both minor V⁴⁺ and major V⁵⁺ ions in contrast to the main valence vanadium oxides.

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