Nonradical Pathway Regulation Through Electronic Structure Modulation for Multifarious Wastewater

The rapid development of single-atom catalysts (SACs) advances water cleanup through the regulation of radical and nonradical pathways; however, the restricted electron utilization efficiency of pollutants still impedes the decontamination. Herein, o-phenanthroline is added to stabilize Fe single atoms over carbon nitride (phen-Fe-CN) with electronic structure modulation, conferring Fe-N₄ acting as a stabilized active center. The selectivity of singlet oxygen (¹O₂) is enhanced in the Fenton system for tetracycline hydrochloride (TH) removal, while it is tuned to the electron transfer pathway (ETP) for electron-rich TH and diclofenac (DCF) with PMS addition. As investigated, the introduction of o-phenanthroline and the formed Fe-N₄ centers are beneficial for modulating the pathway into ETP, with kinetics strongly enhanced both for TH and DCF removal as compared to Fe─CN, as well as delighted removal efficiency with a wide pH range from 1 to 13, sustainable environmental adaptability, and maintained stability. Additionally, o-phenanthroline has been confirmed to intensify charge transfer and raise the deprotonation barrier, thus leading to a preference for PMS to oxidize pollutants via the ETP pathway. A comparison of various systems with the regulation of radical and nonradical pathway is carried out, thus giving a clear understanding of the detailed functional reaction pathway for practical applications.