Characterization of cobalt oxides studied by FT-IR, Raman, TPR and TG-MS

The as-prepared cobalt oxide (assigned as CoOx) was fabricated by precipitation–oxidation from aqueous cobalt nitrate solution using sodium hydroxide and oxidation with hydrogen peroxide. Another series of pure cobalt oxides was refined by the decomposition of CoOx in a nitrogen environment at temperatures of 280, 450 and 950 °C (D-280, D-450 and D-950, respectively). Phase transformation, structural properties and red-ox properties were characterized by thermogravimetry-mass spectrometry (TG-MS), X-ray diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy and temperature-programmed decomposition/reduction (TPD/TPR). Analysis of the thermal behavior on CoOx revealed that a series of pure cobalt oxide with particle sizes of 10–20 nm could be obtained easily. The results demonstrated that the refined samples D-280, D-450 and D-950 were CoO(OH), Co3O4 and CoO, respectively.