Electrochemical Eu(iii) behaviours and Eu oxysulfate recovery over terpyridine-functionalized indium tin oxide electrodes

Abstract

Electrochemical recovery and selective separation of lanthanide (Ln) ions, and thin film fabrication by electrodeposition are very important in view of radioactive waste treatments, the recovery of Ln elements from electronic wastes, and thin film preparation. Herein, we demonstrated the electrochemical behaviors of Eu(III)/Eu(II) ions in NaClO₄ electrolyte over bare and terpyridine (Tpy)-functionalized indium tin oxide (ITO) electrodes by cyclic voltammetry. Amperometry was performed for Eu recovery by electrodeposition. It was found that the Eu(III) ion was recovered as EuSO₄ and Tpy-functionalized ITO showed a higher recovery performance. Eu oxysulfate (Eu₂O₂SO₄) luminescent materials could be obtained by thermal annealing of the electrodeposited samples at 700 °C. The physiochemical properties were fully examined by scanning electron microscopy, high resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction crystallography, Raman spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. Density functional theory was used for geometric optimization and electronic energy state calculation at the B3LYP/GENECP level in the gas and aqueous phases. The present results deepen the role of the functionalized terpyridine ligand in the electrochemical behaviors and recovery of Ln elements.