Spatiotemporal Magnetic Decoupling Directs Spin-Dependent Cascade ROS Evolution for Electro-Fenton Water Decontamination

Heterogeneous electro-Fenton (HEF) systems hold great potential for decentralized water purification, yet concurrently achieving high catalytic activity, structural stability, and controlled reactive oxygen species (ROS) selectivity remains challenging. Herein, we propose a spatiotemporal magnetic decoupling strategy to concurrently address these design objectives. The carbon shell spatially separated exterior Fe0 satellites from the FeNx core, eliminating deleterious short-range magnetic quenching and altering the local magnetic environment to modulate the internal Fe(III) spin state. The resulting low-spin Fe(III) sites suppressed electron back-donation into the H2O2 σ∗ antibonding orbital, favoring an additional 1O2 generation pathway. Spatial decoupling also enabled a gradient cascade activation of H2O2 across the Fe0 and FeNx domains, synergistically boosting the evolution of both •OH and 1O2, with steady-state concentrations reaching 18.25 and 5.27 μM, respectively. Consequently, the FeNx@C-Fe0-based HEF achieved complete naproxen degradation within 60 min with significantly suppressed Fe leaching (0.85 mg L-1), outperforming all comparative systems. Comprehensive characterizations and density functional theory (DFT) calculations established a definitive relationship between topological engineering and spin-state dynamics. Furthermore, the system demonstrated proof-of-concept applicability in real hospital wastewater, highlighting the potential of spatiotemporal spin-state engineering for regulating ROS evolution in HEF systems.