Reduction of Cobalt Oxide (Co₃O₄) by Low Temperature Hydrogen Plasma

Abstract

The paper reports on reduction of cobalt oxide (Co₃O₄) to cobalt metal by low temperature hydrogen plasma. Hydrogen flow rate was varied between 1.167 × 10⁻⁶ to 2.5 × 10⁻⁶ m³ s⁻¹ at a fixed microwave power of 750 W which gave rise to increase in pressure from 1.866 × 10³ to 2.933 × 10³ Pa and increase in temperature of the plasma-cobalt oxide interface from 823 to 1,039 K. Reduction of cobalt oxide to cobalt occurred in steps: Co₃O₄ → CoO → Co. The chemical reaction leading to reduction of cobalt oxide to cobalt is found to be first order with respect to hydrogen flow rate. The activation energy for the first stage of reduction i.e. Co₃O₄ to CoO is found to be 26.2 kJ/mol and that for the second stage reduction of CoO to Co metal is 13.3 kJ/mol.