Thermogravimetric study of the kinetics of Co3O4 reduction by hydrogen

Cobalt(II,III) oxide (Co3O4), synthesized by gel-combustion method, thermally treated in air at temperatures 400, 600 and 800 °C, was subjected to the reduction to metallic state in hydrogen atmosphere. The reduction was carried out at several constant heating rates and controlled by thermogravimetry. The mass vs. temperature curves were analyzed from the kinetic aspect. The two-step reduction was confirmed. Both the hydrogen partial pressure and the sample history influenced the reduction kinetics. The activation energies of both reduction steps were determined by means of Friedman isoconversional method and Kissinger methods, and the values obtained by Kissinger method were used to fit the experimental data by means of expanded Prout–Tompkins reaction model.