Vanadia gel synthesis via peroxovanadate precursors.: 1.: In situ laser Raman and 51V NMR characterization of the gelation process

Vanadium oxide gels derived from aqueous solutions of V2O5 and H2O2 have been investigated using in situ V-51 NMR and laser Raman spectroscopic techniques. On the basis of this characterization, a pathway for peroxovanadate decomposition has been proposed, including the presence of two peroxovanadate dimers. New Raman bands and assignments for these species are reported. Gelation was observed to begin both during and after the peroxovanadate decomposition, depending on the initial molar ratios of H2O2/V and the total concentration of vanadium. Experimental V-51 NMR evidence suggested that the VO2+ species was directly involved in the formation of the gel.