Microporous “order-in-disorder” N-doped biochar via self-template strategy for efficient fenton-like catalysis

Abstract

Constructing defect structures is an effective method to enhance the performance of carbon-based catalysts, but it encounters the deterioration of inherent conductivity. Herein, a micropore-rich N-doped biochar (NBC-3) with an “order-in-disorder” structure is synthesized via an ingenious KHCO₃ intercalation-etching self-templating strategy, which simultaneously incorporates disordered amorphous carbon domains and ordered graphitic carbon ribbons. This strategy endows the nanostructure with abundant carbon vacancies, excellent conductivity and an ultra-high specific surface area (3400 m² g⁻¹). The efficient electron transfer channel on its surface promotes the ultrafast degradation of sulfamethoxazole via peroxymonosulfate activation. The catalyst-dosage-normalized kinetic constant is 23.50 L min⁻¹ g_Cat⁻¹, outdistancing previously reported values. Furthermore, in actual water treatment applications, a tower reactor equipped with only 40 mg of NBC-3 achieved zero SMZ discharge within 1100 min, outperforming conventional catalysts such as Fe⁰, Fe₃O₄, commercial biochar. Density-Functional-Theory calculations reveal that the synergistic effect of carbon vacancies and graphitic N allows the energy released during peroxymonosulfate activation to be stored in the carbon vacancies through surface deformation of the catalyst. This stored energy is subsequently released to promote −HSO₄ desorption, enabling rapid site regeneration and accelerating the reaction. Overall, this study provides a scientific basis for designing efficient metal-free Fenton-like catalysts through molecular-level modulation.