Synergy between Surface Epoxy Groups and Co–C Sites in Nitrogen-Free Single-Atom Catalysts for Electro-Fenton Water Purification

Emerging contaminants, notably antibiotics, pose significant risks to aquatic ecosystems and human health due to their persistence and potential to induce antibiotic resistance. An electro-Fenton (EF) process, utilizing in situ generated hydrogen peroxide (H₂O₂), offers effective pollutant degradation. While current electrocatalysts often suffer from low H₂O₂ selectivity, single-atom catalysts (SACs) have demonstrated superior activity and selectivity. However, their application is limited by poor acidic stability, particularly with nitrogen-coordinated site deactivation under strong oxidation conditions. Herein, a nitrogen-free cobalt single-atom catalyst (BP-Co) was synthesized on defect-rich carbon via ball milling-pyrolysis. BP-Co demonstrates 80% Faradaic efficiency and 10.5 mg cm^-2 h^-1 H₂O₂ yield in acidic media. Both experimental and computational results demonstrate that the presence of surface epoxy groups improves interfacial wettability and electronically tailors the Co-C active sites, thus facilitating *OOH desorption and promoting H₂O₂ generation. In EF applications, BP-Co achieves 100% removal of thiamphenicol (TAP), 77.9% TOC mineralization, continuous Fe²⁺ regeneration, and low energy consumption (0.093 kWh (g TOC)^-1). Moreover, the toxicity of degradation byproducts was significantly reduced. The system performs well across various water matrices and effectively degrades multiple organic pollutants. This study presents a cost-effective, stable strategy for nitrogen-free SACs, advancing water treatment technologies.