Enhanced activation of peroxymonosulfate by ball-milled MoS2 for degradation of tetracycline: Boosting molybdenum activity by sulfur vacancies

Sulfur vacancies on MoS2 enhanced the activation of peroxymonosulfate through the co-existence of radical and non-radical pathways to degrade organic pollutants in wastewater

“…In the case of Mo 3d of MoS 2 , one characteristic peak with 226.80 eV of binding energy appeared, belonging to the sulfur atoms at the end of the Mo–S bond. 30–34 The binding energies located at 229.60 and 232.75 eV corresponding to Mo 3d 5/2 and Mo 3d 3/2 were attributed to the characteristic peaks of Mo( iv ). 32 These peaks were further divided into four small peaks, corresponding to the characteristic phases of 2H-MoS 2 (232.89 and 229.72 eV) and 1T-MoS 2 (232.60 and 229.58 eV).…”

“…It hinted that Mo( iv ) did not act as a main catalytic active site. In previous studies, 30,32–34 most of the researchers considered that Mo( iv ) was in favor of activating PMS. For S 2p of MoS 2 , there appeared two characteristic peaks located at 163.60 and 162.40 eV of binding energy, corresponding to S 2− 2p 1/2 and S 2− 2p 3/2 .…”

“…It hinted that Mo(IV) did not act as a main catalytic active site. In previous studies, 30,[32][33][34] most of the researchers considered that Mo(IV) was in favor of 33 With the increase in temperature, the concentration of S 2À species decreased, and even disappeared at 500 C, whereas the concentration of S I species was remarkably increased. This meant that the oxidation of catalysts was extremely serious.…”

“…The activation of PMS by heterogeneous catalysts containing defect sites has attracted much attention in the past few years. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Among them, the oxygen vacancies are the most studied, 16,[18][19][20][21][22][23][24][25] which oen appear in various catalysts containing oxygen, including pure metal oxides such as Co 3 O 4 16 and ZnO, 19 perovskite 20 and composited compounds. [21][22][23] For example, Zhao et al 16 reported the role of oxygen vacancies in different Co 3 O 4 crystal planes for the activation of PMS by the formation of 1 O 2 ; Gao et al 20 demonstrated the correlation between oxygen-decient sites in the perovskite and the formation of 1 O 2 in activated PMS.…”

“…Sulfur vacancies used for activating PMS have attracted great attention in recent years. [26][27][28][29][30][31] This case is common in transition metal suldes. Compared to oxygen and nitrogen vacancies, sulfur vacancies possess more advantages, as it is not only that the valence-changing transition metal ions are usually good activators for PMS but also that the sulfur defect sites themselves can activate both PMS and metal ions.…”