Engineering single-atom Fe-Pyridine N₄ sites to boost peroxymonosulfate activation for antibiotic degradation in a...

Single-atom Fe catalysts have shown great potential for Fenton-like technology in organic pollutant decomposition. However, the underlying reaction pathway and the identification of Fe active sites capable of activating peroxymonosulfate (PMS) across a wide pH range remain unknown. We presented a novel strategy for deciphering the production of singlet oxygen (¹O₂) by regulating the Fe active sites in this study. Fe single atoms loaded on nitrogen-doped porous carbon (Fe_SA-CN) catalysts were synthesized using a cage encapsulation method and compared to Fe-nanoparticle-loaded catalysts. It was discovered that Fe_SA-CN catalysts served as efficient PMS activators for pollutant decomposition over a wide pH range. Several analytical measurements and density functional theory calculations revealed that the pyridinic N-ligated Fe single atom (Fe-pyridine N₄) was involved in the production of ¹O₂ by the binding of two PMS ions, resulting in an excellent catalytic performance for PMS adsorption/activation. This work has the potential to not only improve the understanding of nonradical reaction pathway but to also provide a generalizable method for producing highly stable PMS activators with high activity for practical wastewater treatment.