S, N, P, and B-doped bio-carbons as dual catalysts for tetracycline degradation via the heterogeneous electro-Fenton process

Bio-carbon (BC) derived from agro-industrial waste was doped with various heteroatoms (S, N, B, P) to evaluate its catalytic performance in the oxygen reduction reaction (ORR) and the electro-Fenton process. The materials were thoroughly characterized using techniques such as nitrogen adsorption at 77 K, carbon dioxide adsorption at -193 K, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Electrochemical performance was assessed via cyclic voltammetry (CV) and linear sweep voltammetry (LSV). All doped samples (S, N, B, P) showed improved ORR activity for hydrogen peroxide generation, with the nitrogen-doped bio-carbon (DBC-N) exhibiting the highest performance. This was attributed to its superior JK value (10.4 mA cm⁻²) and the lowest onset potential (E° onset = -0.14 V). Beyond their ORR catalytic activity, the doped samples were also tested as dual-function catalysts for the degradation of tetracycline via the heterogeneous electro-Fenton process. Notably, all samples achieved enhanced degradation efficiencies (> 40%), with the nitrogen-doped sample reaching a maximum of approximately 70%. This study highlights the potential of producing high-performance, metal-free ORR catalysts through a cost-effective, circular economy-based approach, offering promising applications in environmental remediation, particularly for efficient wastewater decontamination.