Effect of fluoride addition on electrochemical behaviors of V(III) in molten LiCl−KCl

Abstract

X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to analyze the complexes in LiCl−KCl eutectic salt containing VCl3 and KF. The additional fluoride ions would replace chloride ions and combine with V(III) to form VF63−. The electrochemical behavior of V(III) was evaluated under condition of the molar concentration ratio of F− to Vn+ (α) equal to 0:1, 1:1, 2:1, 5:1, 20:1 and 50:1, respectively. The results showed that a new reduction step appeared: VF63−→V2+, and the reduction mechanism of vanadium ions became more complicated. The metallic vanadium was deposited on the tungsten electrode at −2.90 V in the LiCl−KCl melts for 6 h, and the products were characterized by SEM−EDS. It was indicated that the particle size of the product decreased with adding fluoride ions for the forming of the coordination compound VF63−.