Two-step pyrolysis to anchor ultrahigh-density single-atom FeN5 sites on carbon nitride for efficient Fenton-like catalysis near 0?

Low temperatures approaching 0 ? will slash the efficiency of Fenton-like catalysis for organic pollution control. Herein, a two-step pyrolysis strategy is developed to fabricate the carbon nitride nanosheet-supported single -atom Fe catalyst with ultrahigh Fe loading amount of 16.64 wt%. The secondary pyrolysis generates surface vacancies to convert Fe coordination structure from FeN3 to FeN5, which exhibits ultralow activation energy of 6.54 kJ mol-1 in peroxymonosulfate activation for sulfamethoxazole degradation via a new 'surface contact oxidation' path. The catalyst-dose-normalized kinetic rate constant on FeN5 site reaches 21.38 L min- 1 g-1 at 2 ?, even exceeding that on FeN3 site and reported values by 0.61-70.27 time(s) at 25-30 ?. Density -functional-theory calculations reveal that additional N ligands (L) make less charges transfer from Fe toward-SO4 in critical [FeL-SO4] intermediates, enabling their thermodynamically favorable electron seizure from pollutants, and cause easier-SO4H desorption for rapid site regeneration, contributing to excellent low -temperature resistance.

Automated summary

A two-step pyrolysis strategy was developed to fabricate a carbon nitride nanosheet-supported single-atom Fe catalyst with ultrahigh Fe loading amount. The catalyst exhibited excellent performance in organic pollution degradation at low temperatures due to its unique structure and surface vacancies.