Synthesis of lower-valent molybdenum oxides in aqueous solutions by reducing Na₂MoO₄ with NaBH₄

Abstract

Reduction of Na₂MoO₄ with NaBH₄ in aqueous solutions at ambient temperatures has been investigated systematically by varying the concentration and volume of NaBH₄ as well as the reaction pH. The reduction products have been characterized by X-ray diffraction and differential scanning calorimetry (DSC). The reduction yields metastable, amorphous oxides of lower-valent molybdenum, which crystallize around 350 °C to give the binary oxide MoO₂ and the sodium molybdenum bronze Na_0.88Mo₆O₁₇ . The relative amounts of MoO₂ and Na_0.88Mo₆O₁₇ formed are correlated to the overall reducing power that can be achieved. The concentration and volume of NaBH₄ , the reaction pH and the changes in the degree of condensation of the molybdate ions are all found to influence the overall reducing power.

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