Synthesis of Lower Valent Molybdenum Oxides by an Ambient Temperature Reduction of Aqueous K₂MoO₄ by KBH₄

Abstract

Reduction of aqueous K(2)MoO(4) with aqueous KBH(4) at ambient temperatures has been investigated systematically to obtain lower valent molybdenum oxides. Several lower valent oxides such as MoO(2), Mo(4)O(11), K(0.26)MoO(3) (red bronze), K(0.30)MoO(3) (blue bronze), and K(0.85)Mo(6)O(17) are formed during the reduction process; however, only MoO(2) has been obtained as single-phase product. The nature of the product formed is strongly influenced by the reducing power of KBH(4). The reducing power increases with decreasing pH or increasing concentration and volume of KBH(4). The as-prepared samples are amorphous as revealed by X-ray diffraction and transmission electron microscopy. They crystallize sharply at around 350-500 degrees C as revealed by differential scanning calorimetry. Since the products formed are amorphous in nature, they may become particularly attractive for battery electrodes and catalysis.

Synthesis of Manganese Oxides by Reduction of KMnO4with KBH4in Aqueous Solutions

“…2), indicating that the as-prepared samples are nanocrystalline and not amorphous. This is in contrast to the as-prepared samples in the molybdate and tungstate systems, which were found to be amorphous (22)(23)(24).…”

“…Some of these binary oxides were found to be attractive as electrode materials for lithium batteries (20,21). A more systematic investigation of the molybdate (22,23) and tungstate (24), systems reveals that the volume and concentration of the borohydride, the reaction pH, and the degree of condensation of the metalate ions strongly influence the composition of the products. We report in this paper a systematic investigation of the reduction of KMnO with KBH in aqueous solutions with an aim to obtain manganese oxides.…”

Organic assisted hydrothermal route to MoO2/HDA composite microspheres and their characterization

“…Manthiram and co-workers have investigated the reduction of Na 2 MoO 4 with NaBH 4 and similarly, the reduction of K 2 MoO 4 with KBH 4 to synthesize MoO 2 [18]. The instability of the metastable dioxides with low oxidation valence states makes their synthesis difficult in solutions [19,20]. Thus further studies are necessary and challenging for synthesis of lower valent molybdenum oxides through the solution phase route.…”

Hydrothermal Synthesis of the Blue Potassium Molybdenum Bronze, K0.28MoO3

“…Manthiram et al (12,13) reported that, after a heat treatment at 623}773 K of the amorphous products formed by the reduction of K MoO in KBH solution, K MoO , K MoO , and K MoO were crystallized with MoO . We (14}17) also attained formerly by the solid state reactions a series of alkali metal bronzes containing small amounts of MoO by heating hydrated molybdenum bronzes in the neighborhood of 600 K in N atmosphere.…”