Magnetic Fe/Cu Metal–Organic Frameworks-Derived Trilayer Cathode for Enhanced Enrofloxacin Degradation in Heterogeneous Electro-Fenton via Synergistic Radical and Nonradical Pathways

Heterogeneous electro-Fenton (HEF) technology represents a promising eco-friendly strategy for wastewater remediation. However, sluggish Fe(III)/Fe(II) cycling and reliance on a single hydroxyl radical (•OH) pathway limit its overall catalytic efficiency and oxidant utilization. Herein, a bifunctional trilayer cathode (Fe8Cu2@C-GF/ACF) was fabricated by integrating activated carbon fiber (ACF) with a magnetic Fe/Cu metal-organic frameworks-derived layer grown on graphite felt. This architecture spatially couples H2O2 electrogeneration with immediate activation, maximizing the effective utilization of generated oxidants. Furthermore, Cu incorporation thermodynamically accelerates Fe(III)/Fe(II) cycling. The bimetallic synergy facilitates the simultaneous generation of radical (•OH) and nonradical (1O2) species. Quenching and EPR analyses confirmed these dual pathways collectively accelerate enrofloxacin (ENRO) degradation. The system achieves excellent mineralization across a broad initial pH range (3.0 to 9.0). Crucially, effective operation at neutral pH eliminates the need for chemical adjustment. Specifically, treating 100 mg L-1 ENRO at initial pH 7.0 and 18 mA cm-2 yielded a 75.6% mineralization degree. Degradation intermediates were elucidated via DFT calculations and UPLC-QqQ-MS analysis. Finally, the cathode exhibits high stability and low metal leaching. Its intrinsic magnetic recoverability prevents secondary solid waste and promotes practical material reuse for sustainable water treatment.