N-doped carbon nanosheets supported-single Fe atom for p-nitrophenol degradation via peroxymonosulfate activation

• Fe nanoparticle (FeNP) and single Fe atom catalysts (FeSA) were synthesized. • FeSA exhibited 3-fold higher PNP degradation rate and TOF than FeNP. • 1 O 2 and O 2 •− acted as the main oxidative species in the FeSA/PMS system. • FeN 4 was regarded as the active site to promote the activation of PMS. Single atom catalysts with high-catalytic activity have been applied in many fields. In this work, single Fe atoms (FeSA) showed excellent catalytic performance on P-nitrophenol (PNP) degradation with high total organic carbon (TOC) removal rate and high turnover frequency (TOF). The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) results show that Fe species in FeSA are mainly single Fe atom. X-ray absorption near-edge structure (XANES) and density functional theory (DFT) calculations show that each single Fe atom is anchored by four N atoms in the form of FeN 4 active site. This coordination environment enables FeSA possesses unique geometric configuration and highly uniform active sites, which is conducive to organic pollutant adsorption and peroxymonosulfate (PMS) activation. In addition, FeSA could maintained excellent catalytic activity in complex water bodies containing different anions and humic acids. The active species in the FeSA/PMS system were also investigated. It is found that the main oxidative active species in the system are O 2 •− and 1 O 2 . This work shows that FeSA was a highly efficient single atom catalyst for the degradation of organic pollutants and has a wide application prospect in advanced oxidation processes.