Treating the wastes with wastes: Simple preparation of monolithic biomass-derived electrode for enhanced electro-Fenton treatment of pharmaceutical wastewater

The utilization of renewable carbon resources (waste biomass) and the study of metal-free active components have received much attention in the field of catalysis, also showing great development potential for the preparation of electro-Fenton (EF) electrode material toward the efficient wastewater remediation, but there are still many challenges in the revelation of microstructures regulation and EF catalytic mechanism induced by biochar and metal-free active sites. So, in this work, the monolithic biomass-derived electrode (N,P-C/B3C) was prepared by a simple and green strategy, in which the biochar derived from waste bagasse and the heteroatom N, P acted as the carbon-based precursor and the metal-free active sites, respectively. The regulation of electrode microstructure induced by different raw materials was explored. The catalytic performance, stability, energy consumption, toxicity analysis, and organic degradation path in this N,P-C/B3C-EF system were investigated in detail by treating simulated wastewater and real pharmaceutical wastewater, respectively. According to experiments, characterization analysis, and density functional theory (DFT) calculation, the enhanced EF reaction mechanism by the synergistic effect of N,P co-coped sites in carbon matrix was revealed, where Prr N-P and Gra N-P structures may be the suitable sites for 2e- ORR process, accelerating the O2 adsorption and breaking the *-OOH bond to form H2O2. Significantly, Prr N-P possesses the most powerful thermodynamics and the lowest energy barrier toward the rate-determining step (conversion of & sdot;H2O2), being the superior active site for H2O2 adsorption and activation to produce strongly oxidizing ROS.