Electroreduction of Gd3+ on W and Zn Electrodes in LiCl–KCl Eutectic: A Comparison Study

Abstract

This work presents a comparative study of electrochemical properties of Gd3+ on W and Zn electrodes in LiCl-KCl eutectic. It was found that Gd3+ reduction on a tungsten cathode occurs in a single step pattern. Relevant kinetic properties of the Gd3+/Gd redox reaction were investigated by cyclic voltammetry (CV). The reduction of Gd3+ at a liquid zinc electrode in LiCl-KCl-GdCl3 melt and a film zinc electrode in LiCl-KCl-GdCl3-ZnCl2 eutectic were also studied at 773 K. The diffusion coefficient of Gd3+ at the liquid zinc electrode was calculated to be 5.44×10−5 cm2s−1 in LiCl-KCl-GdCl3 melt. The standard rate constants for the charge transfer of Gd3+ at the liquid zinc electrode or on the tungsten electrode was calculated to be about 1×10−2 cms−1 at 773 K by Nicholson method, revealing the redox reaction of Gd3+ to Gd is quasi-reversible based on the Matsuda-Ayabe criteria for practical concept of electrochemical reversibility. Electrodeposition of Gd3+ was carried out on both the film zinc electrode and the liquid zinc electrode. X-ray diffraction (XRD) results showed that intermetallic compounds GdZn12, Gd2Zn17, Gd13Zn58 and GdZn were obtained on the film zinc electrode, whilst intermetallic compound GdZn12 was gained at the liquid zinc electrode. The morphological properties of all the intermetallic compounds were characterized by scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS).