Selective oxidation of electron-rich pollutants in peroxymonosulfate-activated electro-Fenton system: The role of microenvironment-regulated cathode.

Electro-Fenton technologies driven by peroxymonosulfate (PMS) activation have been extensively explored for abatement of organic pollutants from water. Unfortunately, a great diversity of matrix components in contaminated water scenarios inevitably and significantly compromises the efficiency of the generated radicals toward target pollutants. Thus, selective oxidation of the electro-Fenton technologies is urgently desired for cost effective and sustainable water treatment, but challenged by the traditional electron transfer pathway from cathode to PMS to mainly form SO and HO radicals. In this study, we successfully realized selective generation of O, a non-radical species specific for electron-rich pollutants, by regulating the second-shell coordination environment of single-atom Fe in carbonaceous cathode. The doped electron-accepting B drives directional electron transfer from PMS to electrode and inhibiting the undesirable radical pathways. Besides, the electrochemical reduction of H in-situ generated from the dissociation of H-O in PMS is favourable for the formation of O as high as 163.4 μmolLmin. Fast and preferential removal of sulfonamides pollutants in different water matrices demonstrated the excellent matrix tolerance of the newly developed electro-Fenton process. A pilot electrochemical device was designed to further selective remove phenols in real-scenario application. No residual phenol was detected (<0.01 mg/L) with TOC removal around 50% (down to 23.9±0.3 mg L) during the continuous 24-h operation. This study is also believed to shed new light on how to achieve desirable electrochemical reactions via microenvironmental regulation in response to sustainable water decontamination and beyond.