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

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 degrees C to give the binary oxide MoO2 and the sodium molybdenum bronze Na0.88Mo6O17. The relative amounts of MoO2 and Na0.88Mo6O17 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.