Diatomic Fe-Fe catalyst enhances the ability to degrade organic contaminants by nonradical peroxymonosulfate activation system

Atomically dispersed catalysts have been widely studied due to their high catalytic activity and atom utilization. Single-atom catalysts have achieved breakthrough progress in the degradation of emerging organic contaminants (EOCs) by activating peroxymonosulfate (PMS). However, the construction of atomically dispersed catalysts with diatomic/multiatomic metal active sites by activating PMS to degrade pollutants is still seldom reported, despite the unique merits of atom-pair in synergistic electronic modulation and breaking stubborn restriction of scaling relations on catalytic activity. We have synthesized Fe₁-N-C, Fe₂-N-C, and Fe₃-N-C catalysts with monoatomic iron, diatomic iron, and triatomic iron active center, respectively. The results show that the catalytic degradation activity of Fe₂-N-C is twice that of Fe₁-N-C and Fe₃-N-C due to its unique Fe₂N₆ coordination structure, which fulfilled the complete degradation of rhodamine B (RhB), bisphenol A (BPA), and 2,4-dichlorophenol (2,4-DP) within 2 min. Electron paramagnetic resonance (EPR) and radical quenching experiments confirmed that the reaction was a non-radical reaction on the catalyst surface. And singlet oxygen and Fe(IV) are the key active species.