Biochar-based single-atom catalyst with atomically dispersed FeN5 sites (Fe-N-FPBC) is rationally prepared through a micropores construction-functionalization-N doping cascade regulation strategy. The as-synthesized Fe-N-FPBC is rich in micropores and defects which are crucial for effective N doping to achieve FeN5 sites. The electron transfer mediated by Fe-N-FPBC contributes to the ultra-fast degradation of sulfamethoxazole via peroxymonosulfate activation. The catalyst-dosage-normalized kinetic constant is 52.63 L min-1 g-1, outdistancing reported values. Density-Functional-Theory calculations reveal that the FeN5 site exhibits favorable global energy compared to FeN4 site. The axial ligand of FeN5 site results in thermodynamically facilitated electron extraction from contaminants, and also leads to the easier desorption of -SO4H for rapid site regeneration. Overall, this work provides a pathway for the fabrication of biochar-based single-atom catalyst with high metal-N coordination number for efficient Fenton-like catalysis.
