Melamine foam derived nitrogen and boron co-doped metal-free electrode for enhanced electro-Fenton degradation of metronidazole

In this work, a melamine foam derived nitrogen (N) and boron (B) co-doped metal-free electrode was prepared by accessible method and applied in heterogeneous electro-Fenton (EF) system. Overcoming the metal ion leaching and harsh operating conditions of most transition metal electrodes, the prepared metal-free electrode (NB/CF40) possessed an excellent EF performance for degradation of metronidazole (MTZ) in a wide range of pH (3-11), maintaining great reusability even after ten runs with higher mineralized current efficiency (MCE) and lower energy consumption (EC). Significantly, the NB/CF40 has excellent decontamination performance for actual wastewater containing MTZ analyzed by quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs). According to experimental results, characterization analysis and density functional theory (DFT) calculations, EF reaction mechanism by NB/CF40 cathode was proposed, in which the active sites of B-C-C-C-graphitic N and B-C-C-C-pyridinic N configurations contributed to the improvement of EF performance by affecting the charge density of nearby carbon framework, adsorption of O2, and desorption of *OOH. This work offers a new idea for the remediation of wastewater by the efficient metal-free EF system in a wide pH range.