Highly efficient peroxymonosulfate activation on Fe-N-C catalyst via the collaboration of low-coordinated Fe-N structure and Fe nanoparticles for enhanced organic pollutant degradation

Supporting Fe catalysts on N doped carbon (Fe-N-C) renders a promising way towards peroxymonosulfate (PMS) activation for water decontamination, but constructing high-efficiency Fe-N-C remains challenging due to the insufficient understanding of the structure-performance relationship. Herein, the N doped carbon nanotube supported Fe catalysts (Fe-NCNT) were prepared towards PMS activation for organic pollutants removal, in which the Fe-N coordination number and Fe species were tuned through changing the pyrolysis temperature to study their roles in PMS activation. Results showed increasing the pyrolysis temperature converted the Fe-N4 structure in Fe-NCNT to low-coordinated Fe-N3 structure and produced Fe nanoparticles (FeNP, encapsulated in carbon). The Fe-NCNT with Fe-N3 and FeNP exhibited a remarkably high specific activity (0.119 L min−1 m−2), which was 1.8 times higher than that of Fe-NCNT with only Fe-N4 and obviously outperformed those of the state-of-the-art PMS activators. The low-coordinated structure and FeNP promoted the PMS reduction on Fe2+ of Fe-Nx for •OH and SO4•− production, which served as major oxidants for pollutants degradation. The experimental results and theoretical calculation corroborated the low-coordinated structure and FeNP jointly enhanced the PMS adsorption and electron density on Fe center, which accelerated electron transfer from Fe center to PMS for radical production.