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

High-valent iron–oxo species (Fe V =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 Fe V =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 (Fe SA -NPS@C) with FeN 4 active center was synthesized as a highly efficient catalyst for the peroxymonosulfate (PMS)-based oxidation. The Fe SA -NPS@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 Fe SA -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 Fe V N 4 =O with Fe V N 4 =O being the dominant reactive species. Density functional theory calculations revealed that the heteroatom doping effectively altered the electronic structure of the FeN 4 site of Fe SA -NPS@C, which strengthen its coordination with PMS, promote the electron transfer to PMS, and facilitate the interaction between Fe V N 4  = O and OFX, and thus significantly enhanced its catalytic activity. These findings provide new insights into the oxidation mechanism of Fe V =O in heterogeneous systems and the catalytic ability enhancement through heteroatom doping.