A comparative study on catalytic activation of peroxymonosulfate over polytype 2H-MoS2 and 3R-MoS2

MoS 2 polytypes are emerging as compelling metal-sulfide catalysts for peroxymonosulfate (PMS) activation in water decontamination. The catalytic properties of the 1   T and 2H phases have been extensively explored, the performance of the 3   R polytype remains largely unknown. This work presents a comparative investigation of bulk 2H-MoS 2 and 3R-MoS 2 for activating PMS to remove phenol, with a specific focus on the understudied 3   R phase. A ball-milling pretreatment was employed to create sulfur vacancies, a critical active site, in both polytypes. Through a combined experimental and theoretical approach, we demonstrate that sulfur-defective 2H-MoS 2 exhibits superior catalytic activity for PMS activation, with a phenol degradation reaction rate constant 4.3 times higher than that of its 3   R counterpart. More importantly, we unveil that both polytypes activate PMS predominantly via a nonradical pathway mediated by surface Mo-PMS⁎ complexes, rather than generating free radicals. However, in-situ Raman spectroscopy and DFT calculations reveal that the distinct electronic structures of the two polytypes lead to the formation of Mo-PMS complexes with different configurations and oxidative capabilities, explaining their disparate selectivity towards various organic pollutants. This study provides the first mechanistic insight into PMS activation by 3R-MoS 2 and establishes that the crystal polytype is a critical, previously overlooked factor governing the efficiency and oxidation pathway in MoS 2 -based advanced oxidation processes, offering a vital guideline for selecting suitable MoS 2 catalysts in environmental applications.