Abstract: Environmentally friendly iron catalysts have attracted widespread attention in the heterogeneous Fenton-like reaction based on peroxymonosulfate (PMS) for the degradation of emerging pollutants in water, while it has always suffered from the disadvantage of low catalytic activity. Herein, we successfully prepared the magnetic greigite (Fe₃S₄) nanosheet with the exposed {011} facet and rich sulfur vacancies (FS-1) through a simple solvothermal method. The degradation rate of metronidazole by the FS-1 activating PMS under visible light irradiation was 2.93, and 4.48 more than those of the Fe₃S₄ nanosheet with the exposed {011} facet and poor sulfur vacancies, and Fe₃S₄ nanobulk with the exposed {112} facet, respectively. The result of electrochemical analysis and theoretical calculation indicated that the exposed {011} facet of prepared FS-1 offered more active sites to adsorb PMS, and the rich sulfur vacancies on the surface accelerated the electron transfer between oxidants and catalyst. This collaborative effect significantly lowered the energy barrier associated with PMS activation, leading to an increased generation of singlet oxygen. Additionally, the degradation mechanism and pathway of metronidazole, including hydroxyethyl cracking, denitrification, and hydroxylation, were explored in detail through theoretical calculations and high-performance liquid chromatography-mass spectrometry, respectively. This work offers insight into boosting the catalytic performance of environmentally friendly iron-based catalysts.

Key words: Magnetic greigite, Facet, Vacancy, Metronidazole, Fenton-like reaction