Morphogenesis of Highly Uniform CoCO3 Submicrometer Crystals and Their Conversion to Mesoporous Co3O4 for Gas-Sensing Applications

Transition metal nitrates, carbonates, hydroxides, hydroxyoxides, and so forth are often used as solid precursors to synthesize their respective nanostructured metal-oxides after chemical/thermal conversion. However, synthesis of submicrometer uniform crystalline particles of this class of compound intermediates remains as a challenging but less studied area in nanomaterials research. In this work, we report a polyol process for controlled growth of cobalt carbonate (CoCO3). A preparative investigation on morphogenesis of C crystals has been carried out, and three types of highly uniform CoCO3 products (i.e., peanut-like, capsule-like, and rhombus crystals) in the submicrometer region have been synthesized at 200 degrees C under batch conditions. Uniform particles of tricobalt tetroxide (Co3O4) have also been obtained at 300 degrees C from the CoCO3 submicrorneter crystals after thermal transformation in laboratory air. The Co3O4 powder products possess mesoporosity and essentially preserve the pristine morphologies of their respective solid precursors. Due to high crystal uniformity and specific surface areas in the range of 140-149 m(2)/g, the mesoporous Co3O4 exhibits enhanced performances for ethanol and carbon monoxide sensing.