Iron and nitrogen co-doped hierarchical biochar composite cathode for efficient heterogeneous electro-Fenton degradation

Developed a novel iron and nitrogen co-doped biochar composite cathode from jackfruit peel. • This HBC@FeN-C shows hierarchical pores structure. The Fe 3 O 4 nanoparticles provide abundant Fe(III) active sites. • OH is one of the key active species in efficient heterogeneous electro-Fenton degradation. Biochar materials have emerged as promising platforms for heterogeneous electro-Fenton catalysis, yet increase of their catalytic active sites to improve degradation rate remains challenging. Herein, hierarchical porous biochar was functionalized by iron and nitrogen co-doping. Iron was loaded on the surface of carbon matrix in the form of Fe 3 O 4 nanoparticles to provide catalytic active sites, while nitrogen doping may regulate the electronic structure of carbon matrix. Thanks to the combined effect of mass transfer process promoted by hierarchical pore structure and iron and nitrogen synergetic catalysis, the optimized iron and nitrogen co-doped biochar composite cathode showed significantly enhanced catalytic activity in the electro-Fenton degradation of phenol. It achieved 95.4% phenol degradation rate within 180 min under conditions of 0.10 M sodium sulfate electrolyte (current density of 40 mA/cm², pH = 7, catalyst loading of 6.0 mg, 200 mg/L phenol). The corresponding chemical oxygen demand and total organic carbon removal efficiencies reached 62.7% and 75.3%, respectively. It also exhibited good stability, as verified by cycling tests. Electron paramagnetic resonance analysis confirmed that hydroxyl radical radicals are one of the key reactive species involved in phenol degradation. This study demonstrates that iron and nitrogen co-doped hierarchical biochar composite cathode is an effective strategy for treating high-concentration wastewater. Download: Download high-res image (415KB) Download: Download full-size image