Electrochemical Properties of Lanthanum on the Liquid Gallium Electrode in LiCl-KCl Eutectic

Abstract

This work presents an electrochemical study of La(III) in the LiCl-KCl-LaCl3 melt on a liquid gallium electrode. The reduction of the La(III) on a liquid gallium starts at −1.13 V (vs. Ag/AgCl) and is a one step process with three electrons transferred. The activities, activity coefficients and solubilities of La in La-Ga alloys were calculated by open circuit potential technique at the temperature range of 673 to 823 K. Moreover, galvanodynamic methods was also applied on a W electrode to evaluate the apparent standard potential of La(III)/La couple, the Gibbs free energy for the formation of LaCl3 and the activity coefficient of La(III) in the LiCl-KCl-LaCl3 melt. The co-reductive cyclic voltammograms of La(III) and Ga(III) present several redox couples which correspond to the formation and dissolution of different La-Ga intermetallic compounds. Finally, potentiostatic electrolysis was employed to deposit La on a liquid Ga electrode and the intermetallic compound LaGa6 was identified by Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) and X-ray diffraction (XRD) characterizations.