Boosting the efficiency of Fe-MoS2/peroxymonosulfate catalytic systems for organic powllutants remediation: Insights into edge-site atomic coordination

Abstract

Fe atoms were highly isolated by the edge Mo vacancies and the adjacent Mo atoms could provide electrons smoothly for the regeneration of Fe(II). • Fe-MoS 2 catalyst with Fe atomically anchored at the edge Mo vacancies was prepared. • Fe(II) can be rapidly regenerated through the Mo-S 2 -Fe-S 2 -Mo edge configuration. • The electron transfer between edge Mo, S and Fe atoms were well clarified. • Both the adsorption and activation of PMS were systemically investigated. • Fe-MoS 2 was highly stable for the AOPs of varied persistent organic pollutants. Here, we designed and prepared edge defect-rich Fe-MoS 2 nanohybrid catalysts via a facile post-confined strategy, in which single Fe atoms were isolated by the newly formed edge Mo vacancies. Evaluation of the decontamination efficiency, using the model herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), showed that the rate constant for the Fe-MoS 2 /peroxymonosulfate (PMS)/2,4-D system was (0.2777 min −1 ), seven times higher than that of a Fe-MoS 2 nanocluster counterpart (0.0323 min −1 ). The unique Mo-S 2 -Fe-S 2 -Mo edge configuration of Fe-MoS 2 promoted the regeneration of active sites during the activation reaction in which Fe(III) was reduced to Fe(II), Mo(IV) was oxidized to Mo(V), and the adjacent S atoms acted as bridges for electron transfer. Thus, PMS could be constantly activated by low valence Fe atoms resulting in superior catalytic performance. Quenching experiments and Electron Paramagnetic Resonance (EPR) signals indicated that hydroxyl radicals, sulfate radicals (SO 4 •- ), superoxide anion radicals and singlet oxygen ( 1 O 2 ) were all involved in the oxidative degradation of 2,4-D, in which 1 O 2 and SO 4 •- predominated. In addition, PMS adsorption and its activation were identified as key steps in the process, and the Fe-MoS 2 /PMS system demonstrated good robustness during continuous operation. This study provides new insights into the Fe-MoS 2 edge coordination mechanism for the PMS activated decontamination of organic pollutants.