Thermal decomposition analysis of Co2+ content alginic acid cross-linked structure for the synthesis of cobalt oxides

Abstract

A modified sol-gel method employing alginic acid (H-ALG) granule as gelation media was developed for the synthesis of cobalt oxides in this investigation. High-temperature decomposition mechanism of alginic acid was studied using simultaneous thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC), infrared spectroscopy (IR) and mass spectrometry (MS). The main emissions were water, carbon dioxide and carbon monoxide with − 7444.8 J/g heat flow measured at temperatures between 200 and 500 °C. In contrast, the energy released using the cobalt alginate (Co-ALG) sample was determined as − 8296.2 J/g at this temperature range. The oxidation states of the Co-ALG sample gradually changed, resulting in a conversion from Co3O4 to CoO at high temperatures. According to the powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis, single phase cubic Co3O4 were produced with particle size ~25 nm after calcination at 500 °C for 2 h. The ability of H-ALG to attract metal ions, such as Co, could be considered as a low cost and simple route for a large scale production of high purity metal oxides at significantly low temperatures due to the tremendous amount of energy released during the combustion reaction of the alginate structure.