Catalytic activity enhancement by P and S co-doping of a single-atom Fe catalyst for peroxymonosulfate-based oxidation

High-valent iron-oxo species (FeV =O) generated through peroxide activation by Fe-based catalysts can realize the selective and efficient degradation of organic pollutants in water treatment. However, the rapid and efficient generation of FeV =O for the selective degradation of pollutants over a wide pH range with high stability is challenging. In this study, a N, P, and S co-doped Fe-single atom (SA) catalyst (FeSA-NPS@C) with FeN4 active center was synthesized as a highly efficient catalyst for the peroxymonosulfate (PMS)-based oxidation. The FeSANPS@C catalyst exhibited an excellent catalytic performance at low dosages of both the catalyst and PMS for the degradation of pollutants over a wide pH range with high stability. For the degradation of ofloxacin (OFX), the rate constant pertaining to PMS with FeSA-NPS@C was 1.68 min(-1), considerably higher than those obtained using the N-doped and N and P co-doped Fe-SA catalysts. The degradation pathway of OFX revealed that the electrostatic effect was of significance in its degradation by FeVN4=O with FeVN4=O being the dominant reactive species. Density functional theory calculations revealed that the heteroatom doping effectively altered the electronic structure of the FeN4 site of FeSA-NPS@C, which strengthen its coordination with PMS, promote the electron transfer to PMS, and facilitate the interaction between FeVN4 = O and OFX, and thus significantly enhanced its catalytic activity. These findings provide new insights into the oxidation mechanism of FeV =O in heterogeneous systems and the catalytic ability enhancement through heteroatom doping.

Automated summary

In this study, a highly efficient Fe-single atom catalyst (FeSA-NPS@C) was synthesized, which can selectively and stably degrade organic pollutants over a wide pH range with low dosages of the catalyst and peroxymonosulfate (PMS). The heteroatom doping in the catalyst effectively altered its electronic structure, enhanced its coordination with PMS, and promoted the interaction between FeVN4 = O and the target pollutant OFX, resulting in significantly enhanced catalytic activity.