Enhanced Fenton-like degradation over defect-rich bimetallic catalysts: Interfacial electron transfer triggered by coupled FeMn dual-atom-nanocluster sites.

Controllable synthesis of dual-atom-nanocluster (DA-NC) coupled structures offers a new strategy to construct effective catalytic sites and enhance degradation performance in Fenton-like catalysts. In this work, the heteronuclear FeMn DA-NC was fine constructed in a defect-rich Fe/Mn co-doped biochar matrix (Fe/Mn-NABC). Accordingly, Fe/Mn-NABC can effectively activate peroxymonosulfate (PMS) to degrade persistent organic pollutants and generate abundant non-radical species, thereby achieving superior selective degradation (97.9%) with a rate constant of 0.264 min-1, 1.8 times higher than that of Fe monometallic system (Fe-N-C). Electrochemical measurements and DFT calculations reveal that FeMn DA-NC generated via introducing Mn species into Fe-N-C facilitates the interfacial reaction of PMS on the catalyst surface. The electronic modulation shifts the Fe d-band center upward, promotes PMS adsorption, and decreases the reaction energy barrier of PMS activation (1.53→1.11 eV). Furthermore, this system exhibits excellent long-term stability (nearly 100% over 100 h) and prominent economic advantages ($ 0.22/m3). This research offers insights into developing stable Fe-based bimetallic catalysts, revealing the role of structural defect in non-radical catalysis, and optimizing high-efficiency water purification systems.