Synthesis of reduced vanadium oxides in aqueous solutions

Abstract

Reduction of aqueous sodium and potassium vanadates with aqueous ABH₄ (A=Na and K) at ambient temperatures has been investigated systematically to obtain reduced vanadium oxides. Although the as-prepared samples do not show any discernible diffraction peaks, several binary crystalline oxides such as V₂O₃ , V₃O₅ , VO₂ , and V₆O₁₃ , as well as ternary oxides such as Na_0.33V₂O₅ , K_0.23V₂O₅ , and K₂V₃O₈ could be identified after annealing in evacuated sealed silica tubes at 580 °C. The volume and concentration of borohydrides as well as the reaction pH are found to influence the nature of the reaction products. Selected area diffraction of the as-prepared samples in transmission electron microscopy (TEM) indicates that they are nanocrystalline.