Room temperature conversion of X_0.3V₂O₅. nH₂O phase into X2V6O16. nH2O phase Influence of the nature of the cation X⁺

Abstract

Various cations (Li⁺, Na⁺, K⁺, NH₄⁺, Cs⁺, Mg²⁺, Ca²⁺, Ba²⁺) were introduced during the formation of a V₂O₅. nH₂O gel. Cation intercalated X_y V₂O₅. nH₂O (y = 0.3 for X = Li⁺, Na⁺, K⁺, NH₄⁺ or y = 0.15 for Mg²⁺, Ca²⁺, Ba²⁺) were first obtained at room temperature but some of them evolve upon ageing into a new phase: XV₃O₈. nH₂O for X = Na⁺, K⁺, NH₄⁺ and Cs⁺ or XV₆O₁₆. nH₂O for X = Mg²⁺, Ca²⁺, Ba²⁺. All the vanadium oxide phases were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR); the supernatant solutions were analysed by ⁵¹V NMR spectroscopy. These vanadium oxide phases exhibit a layered structure with cations and water molecules intercalated within the interlayer space. The formation of the different phases depends mainly on the pH of the supernatant solution and on the nature of the cation.