Regenerable Cu₂S-CuO heterostructure nanoarray electrode for efficient electrochemical iodate reduction

Effectively removal radioactive iodate (IO₃^-) from aqueous solution is significant for radioactive liquid waste treatment. However, due to the high solubility and mobility of IO₃^-, the removal efficiency of IO₃^- by existing technologies is relatively low. Electrochemical reduction technology is a promising strategy to convert iodine species from high valence states (IO₃^-) to remediable lower valence states (I^-). Herein, a typical Cu₂S-CuO heterostructure nanorod array on copper foam (Cu₂S-CuO@CF) was synthesized by a facile stepwise electrochemical strategy for electrochemical IO₃^- reduction. As the result, the Cu₂S-CuO@CF exhibited a high IO₃^- reduction efficiency of near 100% in 40 min at -1.2 V vs. Ag/AgCl in complicated aqueous solutions ([IO₃^-]_initial = 100 ppm), with a maximum Faradaic efficiency of 98.87% and high IO₃^- removal capacity of over 400 mg g^-1. Electron spin resonance spectra elucidated that the Cu₂S can accelerate the generation of active hydrogen (H*), which is crucial for the subsequent hydrogenation steps during IO₃^- reduction process. Density functional theory calculations revealed that the introduction of Cu₂S on CuO is beneficial for promoting the adsorption of IO₃^- and lowering the energy barrier for IO₃^- reduction. Furthermore, the degraded Cu₂S-CuO@CF electrode had favorable renewability and could revive the ability for IO₃^- reduction. This work presents a compelling strategy for designing and developing high-performance regenerative electrode for the convenient removal of IO₃^- from wastewater, wherein the reduction step is expected to be combined with the downstream immobilization processes to synergistically eliminate IO₃^- pollution.