Fe/Zn Bimetallic-Functionalized Biochar Cathodes for Enhanced Electro-Fenton Performance: Mechanism and...

This study fabricated a novel bifunctional bamboo-derived ZnFe-BC cathode to enhance pollutant degradation in the electro-Fenton process. The prepared cathode exhibited a well-developed porous morphology, a high specific surface area, and abundant active sites originating from iron silicate species. These features enabled high electro-Fenton performance, characterized by sustained H₂O₂ activation and significantly enhanced generation of reactive oxygen species, thereby achieving highly efficient pollutant degradation. Specifically, the cathode delivered an H₂O₂ yield of 13.8 mg L^-1 and removed 95.4% of tetracycline (20 mg L^-1) within 120 min. The Zn/Fe codoping strategy applied in cathode preparation increased the specific surface area, generated abundant active sites, and induced numerous oxygen vacancies (O_v), which contributed to the enhanced cathodic performance in the electro-Fenton process. Mechanistic studies revealed that superoxide radicals (O₂^•-) served as a key intermediate in the two-electron oxygen reduction pathway for H₂O₂ production, whereas hydroxyl radicals (OH^•) acted as the predominant reactive oxygen species responsible for pollutant degradation. Furthermore, the prepared ZnFe-BC cathode demonstrated high stability and reusability even in real complex water matrices, with a degradation efficiency of over 85% and maintained a degradation efficiency of 90% after five consecutive reuse cycles. This work highlights the critical role of bimetallic doping in improving the structural stability and catalytic efficiency of cathodes in the electro-Fenton, providing a promising and sustainable strategy for designing robust biomass-derived bifunctional materials for wastewater treatment.