Breaking through the oxygen hindrance effect in Fenton-like reactions to promote the generation of high-valent iron-oxo species within Fe-NxB/GCN single-atom catalysts

High-valent metal-oxo species (M-oxo), one of the promising non-radical reactive substances for selectively eliminating contaminants from wastewater due to their long half-life and high activity, can be effectively generated in various heterogeneous advanced oxidation processes (AOPs), including those employing singleatom catalysts (SACs) in peroxymonosulfate-based AOPs (PMS-AOPs). However, due to the presence of the oxygen hindrance effect in Fenton-like reactions (OHF), partial transition metal SACs, possessing metal sites with highly occupied state of 3d orbital, are hindered from stable binding with terminal oxygen in PMS to form M-oxo. Herein, B atoms were successfully integrated into Fe SACs (Fe-NxB/GCN) by adopting a two-step calcination method with soft templates. The charge density at Fe sites and the electron filling of Fe 3d orbitals in Fe-NxB/ GCN were effectively reduced after leveraging B atoms, which further lowered energy barrier for generating Fe (IV)=O. The prepared catalysts significantly enhanced the production of Fe(IV)=O in PMS-AOPs and rapidly removed sulfamethoxazole (SMX) from wastewater and source-separated urine, which provided a valuable exploration for modulating the generation of M-oxo by breaking through the OHF effect.