Highly efficient heterogeneous electro-Fenton process enabled by in-situ reconstructed FeNi-foam with high-flux H2O2 generated from gas diffusion electrode

Fe 0.3 Ni 0.7 -foam/ACF cathode coupled with GDE was fabricated to boost HEF performance. • The system realized 98.0% ENRO degradation in 90 min and 77.0% TOC removal in 360 min. • High-flux H 2 O 2 generation well matched the rapid Fe 2+ regeneration. • The final total iron leaching concentration stabilized at 0.53 mg L −1 . Conventional electro-Fenton (EF) technologies suffer from inherent pH sensitivity and massive iron sludge deposition. To address these drawbacks, a gas diffusion electrode integrated heterogeneous electro-Fenton (GDE + HEF) system was fabricated, where a high-flux H 2 O 2 -producing GDE was matched with a Fe 0.3 Ni 0.7 -foam/activated carbon fiber (ACF) composite cathode. This electrode architecture achieves low iron leaching of 0.53 mg L −1 along with high in-situ H 2 O 2 accumulation up to 47.19 mM, greatly outperforming the bare ACF counterpart. Mechanism analysis reveals that H 2 O 2 generated in-situ mildly etches the FeNi-foam substrate and drives the in-situ reconstruction of active iron nanosheets. Benefiting from this integrated design, the rigorous pH limitation of classic Fenton reactions is broken, and favorable catalytic performance with suppressed iron release is sustained over a broad pH window of 3.0–6.5. Under optimized conditions, the GDE + HEF system degrades 98.0% of 100 mg L −1 enrofloxacin (ENRO) within 90 min, with a 77.0% total organic carbon (TOC) removal efficiency after 360 min of reaction. Electron paramagnetic resonance (EPR) and radical quenching tests jointly confirms hydroxyl radicals ( • OH) as the dominant reactive oxygen species responsible for pollutant degradation. Furthermore, the stepwise oxidation pathways of ENRO are elucidated using ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-QqQ-MS). Featuring robust operational stability, the proposed system offers an efficient and practical route for the remediation of pharmaceutical wastewater.