Electrochemical behaviors of Dy(III) and its co-reduction with Al(III) in molten LiCl-KCl salts

Abstract

In this work, the electrochemical behaviors of Dy(III) and its co-reduction with Al(III) on an inert tungsten electrode was investigated in LiCl-KCl molten salts at the temperature of 773K by using cyclic voltammetry (CV), chronopotentiometry (CP) and square wave voltammetry (SWV) techniques. The results showed that the reduction of Dy(III) ions in LiCl-KCl salts is a reversible diffusion controlled process through a one-step reaction: Dy(III)+3e− ↔ Dy(0). The diffusion coefficient of Dy(III) ions was calculated by both the CV and CP methods. Furthermore, the co-reduction of Al(III) and Dy(III) ions on the inert tungsten electrode allows Dy(III) ions to be reduced at a more positive potential through forming Al-Dy alloys. The concentration ratio of Al(III) cations to Dy(III) cations has a large impact on the formation of Al-Dy alloys. In a Dy(III) ion rich system, three signals attributed to the formation of Al-Dy intermetallic compounds were observed in CV and SWV analyses, while only two signals corresponding to Al-Dy intermetallic compounds were observed in the Dy(III) ion poor system. Potentiostatic and galvanostatic electrolyses performed on an aluminum electrode identified the co-reduction by the formation of one (Al3Dy) and two Al-Dy alloys (Al3Dy, AlDy), respectively. Finally, the electrolysis products were characterized by the Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) analyses.