Efficient and safe 4-chlorophenol degradation via redox-tunable dual-membrane electrocatalysis

Electrochemical advanced oxidation processes have shown great potential in water treatment, but controlling toxic intermediates during degradation remains challenging. In this study, an electrocatalytic dual-membrane filtration (EDMF) system with tunable electrode configuration was constructed to regulate the redox sequence in 4-chlorophenol (4-CP) degradation. By alternating the electrode order—anode–cathode (A–C) vs. cathode–anode (C–A)—we systematically investigated the influence of configuration on degradation efficiency, reaction pathway selection, and environmental safety. The dual-membrane systems significantly outperformed single-electrode configurations, achieving over 80% 4-CP removal at 3 V. While the A–C configuration exhibited high ·OH and 1 O 2 -mediated oxidation, the C–A configuration followed a sequential reduction–oxidation mechanism, where cathodic reduction preferentially cleaved the C–Cl bond before anodic oxidation. Quenching experiments, electron paramagnetic resonance, and density functional theory calculations confirmed that the highest occupied molecular orbital / lowest unoccupied molecular orbital distribution of 4-CP rationalizes the pathway selectivity. Although both configurations achieved high dechlorination, the C–A system markedly reduced the accumulation of toxic chlorinated intermediates, leading to lower acute toxicity, mutagenicity, and bioaccumulation potential of transformation products. These findings highlight electrode sequence as a key design parameter to balance efficiency and safety, providing a new strategy for electrocatalytic treatment of halogenated organic pollutants.