Iron single atoms and clusters anchored on natural N-doped nanocarbon with dual reaction sites as superior Fenton-like catalysts

Ultra-small metal clusters have emerged as one of the most promising alternatives to heterogeneous Fenton-like catalysts. Despite the high atom utilization and structural stability of catalysts with ultra-small clusters and single-atom sites, there is still challenging for the synthesis of these catalysts due to their facile aggregation. Herein, we successfully fabricated a catalyst (Fe-NC-900) with single-atom sites and ultra-small clusters by a ball milling method combined with subsequent pyrolysis process. Fe-NC-900 showed high efficiency and superior stability in the activation of peroxymonosulfate (PMS) for catalytic oxidation of refractory organic compounds. Chemical quenching experiments, electron paramagnetic resonance (EPR), in-situ Raman spectra, and electrochemical analysis indicated that the 1O2 oxidation was the main non-radical pathway rather than the high-valent iron oxidation and electron transfer mechanism for the degradation of RhB in the Fe-NC-900/PMS system. This work provides useful insights into the design and synthesis of the catalysts with single atoms and ultra-small clusters for practical applications in Fenton-like catalytic processes.