Preparation of reduced molybdenum oxides (MoO2MoO3) by a sol-gel method

Molybdenum oxides were prepared by a sol-gel method using molybdenum chloro-ethoxide as a precursor. MoCl5, ethanol and potassium metal were used as starting materials. KCl by-product was filtered out. All reactions proceeded in methane dichloride solvent at room temperature. Blue amorphous precipitates which look like “molybdenum blue” were obtained after evaporation of solvent. This product crystallized to MoO3 on heating to 300 °C in air, to MoO2 on heating in vacuum and to Mo4O11 together with MoO3 and MoO2 when heated in He gas. The valence of molybdenum in the blue, as-prepared sample, ranges from 4 to 6 and could not be determined unambiguoulsy by IR and XPS spectra. The molybdenum oxide products incorporated 25–35 wt% of physically adsorbed solvent and/or reaction product (H2O, C2H5OH) and retained ethoxy and hydroxyl groups; the adsorbed species and retained ethoxy groups are lost on heating at ∼200 °C and at ∼400 °C, respectively. About 1–6 wt% of chlorine was also retained in the product, most of which was removed on heating to 160 °C in air.