Electrolytic Reduction of ZnO in the CaCl₂-NaCl Molten Salt

Abstract

Electrolytic reduction technology plays a significant role in industrial metal production. In the present work, cyclic voltammetry and square wave voltammetry were applied to study the electrochemical behaviors of ZnO cathode in the CaCl2-NaCl melt at 873 K. During the experiment, we found that the dissolution-electrodeposition mechanism (ZnO = Zn2+ + O2-, Zn2+ + 2e- = Zn) dominates the electrolytic reduction of ZnO, and the contribution of the direct-reduction from solid phase (ZnO + 2e- = Zn + O2-) is small. Furthermore, the electro-reduction of ZnO was conducted by potentiostatic electrolysis. The peak potential of ZnO to Zn was -0.48 V vs Ag/Ag+. Therefore, the metallic Zn can be obtained at an applied potential of -0.80 V (vs Ag/Ag+). When the applied potential increased to -2.00 V (vs Ag/Ag+), the Zn and CaZn3 alloy were formed simultaneously. The electrolytic products were confirmed by X-ray diffraction analysis. This study proved the feasibility of electro-reduction technology to prepare Zn metal through the reduction of ZnO material.