Green production of nickel powder by electro-reduction of NiO in molten Na2CO3-K2CO3

Nickel powder was directly prepared in a molten Na2CO3-K2CO3 electrolytic cell at 750 °C. In the molten bath, porous NiO pellets were acted as the cathode and Ni10Cu11Fe alloy was applied for oxygen gas evolution anode. The electrochemical reduction of NiO was determined to follow a one-step reduction mechanism by cyclic voltammetry measurements and potentiostatic electrolysis combined with XRD analysis and EDX tests. Furthermore, two-electrode constant voltage electrolysis under different cell voltage was conducted to optimize the energy efficiency and product quality. A relatively low energy consumption of 1.05 kWh for production 1 kg nickel powder was achieved under 1.1 V with a current efficiency of 95.4%. The present work demonstrates a “green” and energy efficient nickel production way and further evidences that molten carbonate electrolysis (MCE) can be an environmental sound technology for metal production.