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

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