Electrochemical Behavior of Niobium Ions in Molten KCl-NaCl

The reduction mechanism of Nb(V) in molten KCl-NaCl at 1023 K was investigated by a series of electrochemical techniques such as cyclic voltammetry, square wave voltammetry and chronopotentiometry. It was found that there were three steps in the reduction of Nb(V) as Nb(V)→Nb(III)→Nb(I)→Nb, and electrochemical reaction, Nb(V)→Nb(III), is a quasi-reversible diffusion controlled process. The diffusion coefficient of Nb(V) was also obtained by cyclic voltammetry, square wave voltammetry and chronoamperometry. The relationship between current density and the square root of time shows that the nucleation of niobium belongs to the instantaneous nucleation on molybdenum electrode in molten KCl-NaCl-NbCl5 (0.43 × 10−3 mol/cm3) at 1023 K at −3.10 V vs. Cl2/Cl−. Moreover, the metallic niobium was deposited on molybdenum wire by chronoamperometry, and the products were analyzed by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). The results showed that the metallic niobium has a high purity of 99.98%.