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.