Electrodeposition of neodymium from betaine-ethylene glycol deep eutectic solvent using neodymium oxide as a precursor

Abstract

The electrodeposition of neodymium was investigated in betaine-ethylene glycol (Bet-EG) deep eutectic solvent (DES) containing neodymium oxide (Nd2O3) at different temperatures ranging from 353 K to 373 K. The electrochemical behavior of Nd2O3 dissolved in Bet-EG DES was researched by cyclic voltammetry, potentiodynamic polarization and chronoamperometry methods. Cyclic voltammograms (CVs) manifest that Nd(III) reduction in Bet-EG is an irreversible process with diffusion-controlled, and the reduction overpotential of Nd(III) decreases with the increase of the temperature. The temperature has an impact on the diffusion coefficient of Nd(III) species, obeying the Arrhenius equation. The activation energy is estimated to be 36.78 kJ mol−1. The cathodic polarization analysis shows that the rise of temperature promotes the reduction of Nd(III). The UV–Vis and ESI-MS analyses show that [Nd2(bet)8(H2O)4]6+ complex anions are formed as Nd2O3 is dissolved in Bet-EG DES. Electrodeposited neodymium with various morphologies were characterized and analyzed by EDX, XPS, XRD and SEM. It is found that the electrodeposition temperature has a great effect on the morphology of Nd electrodeposits. Depending on the deposition temperature, metallic Nd with submicron particles or porous structures were obtained.

Keywords

• Electrodeposition
• Bet-EG
• Nd2O3
• DES
• Nd