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 SO4•- and HO• radicals. In this study, we successfully realized selective generation of 1O2, 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 1O2 as high as 163.4 μmol.L-1min-1. 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-1) 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.