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 CoFe-LDHs/NF, and promotes the binding affinity of Co sites for surface complexed PMS and ROS. The introduced Fe/Fe couple also facilitates Co/Co redox cycle for PMS activation. The monolithic CoFe-LDHs/NF catalyst demonstrates 20 % enhancement in catalytic efficiency than pure Co-LDHs/NF for sulfisoxazole oxidation. Additionally, it exhibits 1.45 to 7.47-fold higher apparent rate constant than Co-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 as predominant key species. A continuous flow-through CoFe-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.