Photo-enhanced in-situ Fenton/Fe-C micro-electrolysis for efficient COD reduction: D-band center reverse regulation boosts Fe²⁺ regeneration

Fe-C micro-electrolysis coupled with in-situ Fenton reaction serves as a critical pretreatment process for refractory wastewater, yet faces bottlenecks such as low Fe²⁺ regeneration efficiency and Fe³⁺ accumulation-induced reaction termination. Herein, a floating photoelectrochemical synergistic system was constructed. By reversely regulating the D-band center of Fe in the photoanode (downshifted by 0.27 eV), the reduction of Fe³⁺ to Fe²⁺ was significantly accelerated. Results demonstrate that under pH = 2 conditions, the system achieved directional migration and temporary storage of photogenerated electrons, driving in-situ hydrogen peroxide (H₂O₂) generation via Fe-C micro-electrolysis and activating hydroxyl radicals through Fenton reactions. Moreover, under day-night cycles, the system maintained ≥50% COD removal for over 5 days and achieved 89.2% cost saving compared to the traditional Fe-C/Fenton process. This study provides an efficient and stable solution for Fe-C micro-electrolysis/Fenton technology, with theoretical innovation in D-band center regulation and practical potential.