Comprehensive consideration of screening fluoride electrolyte for electrodeposition of rare earth cerium

Abstract

Molten salt is an indispensable medium for the electrochemical extraction of rare earth metal cerium (Ce). However, the existing molten salt system is incapable of meeting the low-cost requirement of industrial production. The selection of molten salt electrolyte is closely related to its thermodynamic properties and its influence on electrolytic extraction in terms of electrochemical reaction and kinetics. Herein, the constructed potential fluoride electrolyte systems (CeF₃-LiF-BaF₂, CeF₃-LiF-NaF, CeF₃-LiF-KF, and CeF₃-LiF-NaF-KF melts) were systematically investigated with respect to theoretical electrochemical window, exchange current density at the molten salt/electrode interface during electrolytic reduction, and the effect of density in rare earth deposition. From a comprehensive point of view, the choice of molten salt system for electrolysis should combine the electrochemical reaction properties of rare earth metal ions in it and the physicochemical properties of the molten salt itself. The CeF₃-LiF-BaF₂ electrolyte was considered as the most promising molten salt system due to its various outstanding parameters (diffusion coefficients: 6.74×10⁻⁷ cm² s⁻¹, exchange current density: 0.649 A cm⁻², density: 4.046 g·cm⁻³). This work provides new insights into fluoride electrolyte design screening.