Generation of FeIV=O and its Contribution to Fenton-Like Reactions on a Single-Atom Iron-N-C Catalyst.

Abstract

Generating FeIV=O on single-atom catalysts by Fenton-like reaction has been established for water treatment; however, its generation pathway and oxidation behavior remain obscure. Here, using a Fe-N-C catalyst with typical Fe-N4 moiety to activate peroxymonosulfate (PMS), we demonstrate that generating FeIV=O is mediated by the first-formed Fe-N-C-PMS* complex, a well-recognized nonradical species inducing electron-transfer oxidation, and determined by the adjacent Fe sites with specific Fe1-Fe1 distance. After the Fe atoms with Fe1-Fe1 distance <4 Å are PMS-saturated, Fe-N-C-PMS* formed on those with Fe1-Fe1 distance of 4-5 Å can coordinate with the adjacent FeII-N4, forming an inter-complex with enhanced charge transfer to produce FeIV=O. FeIV=O enables the Fenton-like system to efficiently oxidize various pollutants in a substrate-specific, pH-tolerated and sustainable manner, where its prominent contribution manifests for the pollutants with higher one-electron oxidation potential.