Electrochemical studies on cerium(III) in molten fluoride mixtures

This study aims to determine the principal electrochemical characteristics of the electrodeposition of cerium metal from molten fluoride systems. The cathodic process of Ce3+ ions in LiF-NaF and LiF-NaF-CaF2 molten salts was studied using electrochemical techniques as steady state and cyclic voltammetry methods. The decomposition potential (Ed) and the overvoltage(η) were determined for NaCeF4 using current-potential curves under galvanostatic conditions. The Ed was found to be 2.025 V in LiF-NaF and 2.045 V in LiF-NaF-CaF2. It was also found that the ohmic drop potential (EΩ) was not dependent on NaCeF4 concentration and it rose as the current intensity increased. The overvoltage (η) was determined from the polarization curves and the Tafel coefficients and kinetic parameters were calculated on the assumption that the process constitutes of direct discharge of Ce3+, with no solvent-solute interaction. In order to elucidate the cathodic process the investigation by cyclic voltammetry technique was finally used. From the evolution of the voltammograms we concluded that the electrochemical reduction of Ce3+ ion was actually a reversible process on the molybdenum electrode and cathodic reduction of Ce3+ took place in one single step involving three electron exchanges.