Spin-Regulated Fe-Cu Diatomic Catalytic Chemistry Enables Significant Minimization of Catalyst Consumption With High-Efficiency Fenton-Like Activity

The high cost and limited metal loading of single-atom catalysts hinder their broader applications in Fenton-like reaction for water treatment. Herein, we developed an Fe-Cu diatomic catalyst supported on N-doped carbon (Fe-Cu-CN) that enabled catalyst minimization while maintaining high peroxymonosulfate (PMS) activation efficiency. By tailoring asymmetric Fe-Cu coordination and inducing a spin-state transition of Fe from low-spin to high-spin, the catalyst enhanced Fe 3d-O 2p electron coupling and substantially improved intrinsic activity. The Fe-Cu-CN/PMS system enabled a highly efficient electron transfer pathway for pollutant degradation, achieving rapid bisphenol A removal (100% within 5 min; k_obs = 1.61 min^{- 1}) with only 10%-20% of the catalyst dosage commonly reported in the literature. Density functional theory calculations and electrochemical analyses revealed that heteronuclear coordination modified the spin-state of the active center, narrowing the gap between the d-band center of Fe 3d orbitals and the Fermi energy level to strengthen the electronic interaction at the reaction interface, resulting in a lower free energy barrier of PMS adsorption thermodynamically. Furthermore, the life-cycle analysis demonstrated superior environmental performance. This study provides a generalizable strategy to enhance unit catalytic activity through spin-state engineering, offering practical potential for PMS-based water treatment.