Tuning the electron structure of single-atom Fe catalyst for designed peroxymonosulfate activation and phenols degradation

Transition metal single atom catalysts (SACs) for boosting peroxymonosulfate (PMS) activation involving complex catalytic mechanism and multiple reaction pathways have received much attention, but regulating the reaction pathway of SACs is still an important challenge in the PMS-mediated Fenton-like reaction. Herein, a boron-doped Fe SAC with FeN₃B configurations (Fe-BNC) was synthesized and selectively generated a non-radical pathway, in which the high-valent iron-oxo species (Fe^IVO) was determined as the main reactive oxygen species (ROS) by PMS activation. The FeBNC/PMS system not only exhibited remarkable reaction kinetic constant (0.949 min⁻¹) and turnover frequency (9.49 L min⁻¹g⁻¹) for the phenol degradation, but also showed excellent selectivity to phenols with strong electron-donating ability. Mechanism exploration based on theoretical calculations revealed that high activity of FeBNC originated from the reinforced adsorption energy and enhanced overlap between Fe 3d and O 2p orbits, which facilitated to strengthen the FeO bonding and accelerate the electron transfer, thus modulating the PMS activation via a non-radical pathway. Successful extendibility of FeBNC in treatment of the real water and coking wastewater demonstrates its application potential. This work elucidates the mechanism of selectively generating a non-radical pathway over B-doped Fe-based SAC, and provides a rational strategy for preparing SACs alone with a non-radical pathway.