Studies on Cerium Electrochemistry in High Temperature Ionic Liquids

The cathodic behavior of Ce3+ ions in LiF-NaF-BaF 2, LiF-NaF-NaCl and NaCl-KCl molten salts at 730 degrees C has been studied using different electrochemical techniques. The decomposition potential (E-d) and the cathodic overvoltage were determined by introducing NaCeF4 as electrochemical active species using steady-state potential-current curves recorded under galvanostatic conditions. The values of vertical bar E-d vertical bar were 1.85 V in LiF-NaF-BaF2 2, 2.114 V in LiF-NaF-NaCl and 2.538 V in NaCl-KCl, respectively. It was also found that the ohmic drop potential in melt is not dependent on NaCeF4 concentration and it rises as the current intensity increases. The Tafel slopes and other kinetic parameters were calculated on the assumption that the cathodic process consisted of direct discharge of Ce3+, with no solvent-solute interaction. In order to elucidate the mechanisn of cathodic process the cyclic voltammetry technique was finally used. From the evolution of the voltammograms we conclude that the electrochemical reduction of Ce3+ ion is actually a reversible process on the molybdenum electrode and cathodic reduction of Ce3+ takes place in one single step involving three electron exchange. Our study adds to the accumulating data and confirms available results of electrodeposition of metalic cerium from molten salts using NaCeF4 as solute.