Investigation of the reduction process of Nd(III) ions on tungsten electrode in LiF-NdF3-Nd2O3 molten salt at 1323 K

Rare-earth metal neodymium is an important raw material for NdFeB permanent magnets, and its demand has significantly increased in recent years. Molten salt electrolysis is the main method for the production of metal neodymium, so the study of the electrodeposition process of neodymium ions in molten salt at the cathode is of great significance for the production of metal neodymium. In this paper, the electrochemical deposition process of neodymium ions on a tungsten working electrode was studied in a LiF-NdF 3 -Nd 2 O 3 molten salt system using electrochemical methods such as cyclic voltammetry and open circuit potential. Additionally, the influence of LiF content in the molten salt on the electrodeposition process was analyzed. The experimental results indicate that the reduction of neodymium ions in the LiF-NdF 3 -Nd 2 O 3 molten salt system consists of two stepwise quasi-reversible redox reactions: Nd(III) → Nd(II) and Nd(II) → Nd(0). The corresponding reduction peak potentials are −0.78 V and −1.19 V, respectively. The Nd(III) → Nd(II) reaction is solely diffusion-controlled, while the Nd(II) → Nd(0) reaction is governed by both surface control and diffusion control in the electrochemical process. The increase in LiF content in the molten salt leads to a shift of the cathodic overpotential in the positive direction. When the LiF content is high, the reduction of neodymium ions on the electrode becomes unstable, making it unfavorable for the deposition of metal neodymium on the tungsten electrode.