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.