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

Here, we designed and prepared edge defect-rich Fe-MoS2 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-MoS2/peroxymonosulfate (PMS)/2,4-D system was (0.2777 min−1), seven times higher than that of a Fe-MoS2 nanocluster counterpart (0.0323 min−1). The unique Mo-S2-Fe-S2-Mo edge configuration of Fe-MoS2 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 (SO4•-), superoxide anion radicals and singlet oxygen (1O2) were all involved in the oxidative degradation of 2,4-D, in which 1O2 and SO4•- predominated. In addition, PMS adsorption and its activation were identified as key steps in the process, and the Fe-MoS2/PMS system demonstrated good robustness during continuous operation. This study provides new insights into the Fe-MoS2 edge coordination mechanism for the PMS activated decontamination of organic pollutants.