Vanadium pentoxide based xerogels, H₂V₁₂O_31-y∙nH₂O, have been extensively studied over past years because of their particular properties. These materials can be used as reversible cathodes in lithium batteries, electrochromic layers for display devices, host materials for the intercalation of guest species, humidity sensors, starting material for switching elements, and so on. These xerogels have a layered structure where V₂O₅ chains are bonded by interlayer water, and can intercalate guest ions and molecules.

Partial substitution of vanadium ions by a metal of higher valence (Mo, Cr) in hydrated vanadium oxides leads to a decrease of the electronic part of conductivity. The X-ray photoelectron spectroscopy (XPS) spectra of hydrated vanadium oxides
(VO)Mo_xV_12-x×nH₂O (X = 0, 1, 2, 3) has been studied to provide the vanadium ions reduction ratio RR = V⁴⁺/(V⁴⁺+V⁵⁺) dependence on the molybdenum ions concentration and the thermal treatment. The analysis of vanadium and molybdenum XPS spectra of the thermally untreated samples demonstrate that either V 2p_3/2 and Mo 3d_5/2 lines shape is actually independent on the molybdenum concentration within 0 ≤ x ≤ 3 interval. It was shown, that RR » 0.18 is same that for the all tested samples, while molybdenum is in the main Mo⁶⁺ oxidation state. It indicates that charge transfer V⁴⁺+Mo⁶⁺ ↔ V⁵⁺+Mo⁵⁺ between V and Mo ions do not take place. The temperature desorption mass spectroscopy analysis shows that for (VO)V₁₂×nH₂O xerogel intensive desorption of oxygen from xerogels begins at T_k ≈ 460K. The significant, of about 0.13, increase of vanadium ions RR for the samples backed below and above T_k may be related with an appearance of additional O^2- vacancies due preferential oxygen evaporation above T_k.

It was concluded that the appearance of V⁴⁺ ions in V₂O₅-based xerogels is mainly related with the stoichiometry of the samples, while higher valence admixture ions acts only as a diluting component.

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