High-efficiency and sustainable peroxymonosulfate activation on Fe single-atom catalyst through incorporating...

Single-atom FeNC catalyst is a promising alternative for peroxymonosulfate (PMS) activation based water treatment, but the trade-off between PMS adsorption and products desorption on Fe single site limits its performance for achieving sustainable PMS activation. Herein, the thiophene-like S (CSC) and oxidized S (C-SO_x) with different electron-donating/withdrawing properties were introduced into the second coordination shell of single-atom FeNC catalyst (Fe-NSBC) to optimize its Fe electronic structure for high-efficiency and sustainable PMS activation. The S species composition was also regulated to study its effect on catalytic performance and mechanism of Fe-NSBC. Results showed the Fe-NSBC displayed highest PMS catalytic efficiency and radical (SO₄^•- and •OH) yield at moderate CSC/C-SO_x ratio, whose catalytic activity was 3.8 and 21.1 times higher than that of Fe-NBC without S doping and homogeneous Co²⁺ (metal-based benchmark), and greatly outperformed those of the state-of-the-art FeNC based catalysts. Moreover, the Fe-NSBC/PMS favored free radicals production for preferential removal of hydrophilic pollutants, and displayed unique anti-interference and long-term effectiveness in real water decontamination. The CSC and C-SO_x played complementary role in promoting sustainable PMS activation: CSC raised d-band center and electron density of Fe for enhanced adsorption and reduction of PMS into radicals, while C-SO_x lowered d-band center of Fe for favorable radical desorption and active site regeneration.