Effects of F− ions on the electrochemical and interface behavior of cathodes in zinc electrowinning

Abstract

The increasing use of Zn metal in the energy and industrial sectors necessitates a higher level of research into the zinc electrowinning process. In this work, the effects of fluoride ions (F−) in zinc electrolyte on the cathodic kinetics and zinc product quality during zinc electrodeposition was systematically investigated via a series analysis. The results revealed that the addition of F− in the electrolyte showed a polarization effect, with an increase in the apparent cathodic exchange current density increased by 104 orders of magnitude, and a decrease in the zinc deposition overpotential by 46 mV at a concentration of 400 mg/L. However, F− also reduces the hydrogen evolution overvoltage, when the electrolyte contains 400 mg/L F−, the hydrogen evolution overvoltage on aluminum cathode and zinc cathode decreases by 121 mV and 97 mV, respectively. The promoted hydrogen evolution kinetics increases energy consumption and surface porosity. Additionally, F− ions corrode the Al2O3 oxide film on the cathode surface, accelerating the corrosion of the aluminum cathode plate. This results in increased adhesion of zinc deposition to the damaged aluminum substrate, making it difficult to peel off.