Electrochemical behavior and electrolysis of VCl3 in molten LiCl-KCl eutectic salts on tungsten electrode

Abstract

This paper investigated the electrochemical behavior of V(III) on W electrode using cyclic voltammetry (CV), square wave voltammetry (SWV), and open circuit chronopotentiometry (OCP) at 773 K in LiCl–KCl molten melt. The results indicated that the reduction process of V ions in LiCl-KCl molten salt was a two-step reaction: V(III)→V(II)→V(0). The diffusion coefficient of V ions was determined through cyclic voltammetry, square wave voltammetry, and convolution voltammetry, with all values found to be on the order of 10⁻⁵ cm² s⁻¹. The standard rate constant k⁰ and the transfer coefficient α were also evaluated using convolutional voltammetry. Thermodynamic properties, including the Gibbs free energy of formation, standard enthalpy, and entropy of VCl₂, were calculated using open-circuit chronopotentiometry over the temperature range of 693–813 K. Electrodeposition was performed at − 2.30 V, − 2.70 V, − 2.90 V, and − 3.10 V vs. Cl₂/Cl^- on the W electrode by two- or three-electrode system and the resulting cathodic products were characterized using XRD and SEM-EDS. The main component of the deposition product was metallic vanadium. As the applied potential shifted negatively, the vanadium extraction efficiency increased. The highest extraction efficiency was more than 99.50 %, with a current efficiency of 86.37 % under the two-electrode system.