Single-Atom Mn–N₄ Catalyst with Electron-Rich O and S Self-Doping for Cooperative Nonradical and Radical Oxidation: Overlooked Nonmetal Heteroatomic Sites

Abstract

Exploring the role of nonmetal heteroatoms doping in single-atom catalysts for peroxymonosulfate (PMS) activation is highly significant for understanding and developing PMS activators. Herein, a novel single-atom Mn (Mn–N4) catalyst with electron-rich O, S self-doping (MnSA–N–CO,S) was synthesized via a facile and scalable impregnation-annealing method, which exhibited admirable capability to activate PMS for ibuprofen (IBU) degradation with a reaction constant as high as 0.225 min–1 (10.32 times higher than the carbon matrix). It was verified that Mn–N4 played a strong adsorption capacity for PMS to facilitate the electron transfer (Mn2+/Mn3+ cycle) for PMS activation via a nonradical process (1O2 dominated), and the electron-rich O, S active sites on the carbon skeleton made a joint contribution on IBU degradation via a radical process (·OH, SO4·–, and O2·– dominated). Under this cooperative activation system, the MnSA–N–CO,S exhibited impressive environmental resistance and reusability for IBU removal, as well as universality toward various pollutants with considerable mineralization efficiency. This study provides new insights into the cooperative role of overlooked nonmetal heteroatoms in single-atom catalysts for PMS activation toward refractory organics degradation.