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

Reduction of Na 2 MoO 4 with NaBH 4 in aqueous solutions at ambient temperatures has been investigated systematically by varying the concentration and volume of NaBH 4 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 MoO 2 and the sodium molybdenum bronze Na 0.88 Mo 6 O 17 . The relative amounts of MoO 2 and Na 0.88 Mo 6 O 17 formed are correlated to the overall reducing power that can be achieved. The concentration and volume of NaBH 4 , the reaction pH and the changes in the degree of condensation of the molybdate ions are all found to influence the overall reducing power.