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

Nickel powder was directly prepared in a molten Na2CO3-K2CO3 electrolytic cell at 750 degrees 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. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.