Oriented near-surface catalytic oxidation through strengthening surface-localized radical generation over CoFe bimetallic sites: Synergistic mechanism and electro-assisted regeneration

Nanocatalysts-catalyzed heterogeneous advanced oxidation process offers a promising option for decentralized wastewater treatment, whereas free reactive oxygen species (ROS) suffer from ultrashort lifetime and self-quenching effect. Herein, bimetallic CoFe-layered double hydroxide nanorods are synthesized over three-dimensional conductive nickel foam (CoFe-LDHs/NF) to achieve high proportion of surface-localized ROS by peroxymonosulfate (PMS) activation. The Fe incorporation motivates electron redistribution of Co–Fe dual metal sites in stoichiometrically-optimized Co 2 Fe 1 -LDHs/NF, and promotes the binding affinity of Co sites for surface complexed PMS and ROS. The introduced Fe 2+ /Fe 3+ couple also facilitates Co 2+ /Co 3+ redox cycle for PMS activation. The monolithic Co 2 Fe 1 -LDHs/NF catalyst demonstrates 20 % enhancement in catalytic efficiency than pure Co 3 -LDHs/NF for sulfisoxazole oxidation. Additionally, it exhibits 1.45 to 7.47-fold higher apparent rate constant than Co 3 -LDHs/NF for benzoic acid oxidation with extending premixing period of catalyst and PMS (from 0 to 15 min), largely attributed to 64.9 % surface-localized ROS. Electron paramagnetic resonance, radical scavenging test, and probe experiment validate surface-localized SO 4 − as predominant key species. A continuous flow-through Co 2 Fe 1 -LDHs/NF catalytic system achieves >85 % BA removal over 900 min via single-pass operation, with electro-assisted regeneration at appropriate bias voltage. The proposed strategy provides new insights on designing oriented near-surface oxidation mode for long-term stable decontamination.