Abstract
In this research, ab initio calculations and experimental approach were adopted to reveal the mechanism of Hg0 adsorption on MoS2 nanosheets that contain various types of defects. The ab initio calculation showed that, among different structural defects, S vacancies (Vs) in the MoS2 nanosheets exhibited outstanding potential to strongly adsorb Hg0. The MoS2 material was then prepared in a controlled manner under conditions, such as temperature, concentration of precursors, etc., that were determined by adopting the new method developed in this study. Characterisation confirmed that the MoS2 material is of graphene-like layered structure with abundant structural defects. The integrated dynamic and steady state (IDSS) testing demonstrated that the Vs-rich nanosheets showed excellent Hg0 adsorption capability. In addition, ab initial calculation on charge density difference, PDOS, and adsorption pathways revealed that the adsorption of Hg0 on the Vs-rich MoS2 surface is non-activated chemisorption.
Highlights
The airborne elemental mercury (Hg 0) is the most dominant and problematic form of mercury[1,2,3] because it is highly volatile and insoluble in water [4,5,6]
The MoS2 nanosheets normally contain different structural defects in its crystal lattices, which are the potential sites for airborne Hg0 capture [41].The MoS2 nanosheets with defect-free surface as well as those with different types of defects, such as vacancies with the absence of one S atom (VS), the absence of two S atoms (VS2) and the absence of one Mo atom (VMo), were investigated in detail in this study
It is found that the atoms around the S vacancy exhibit different extents of inward relaxation depending on the number of S atoms that are absent
Summary
The airborne elemental mercury (Hg 0) is the most dominant and problematic form of mercury[1,2,3] because it is highly volatile and insoluble in water [4,5,6] It can travel in the air over a long-distance, bio-accumulate in the ecosystem and is persistent in the environment [7]. Different types of defects in MoS2 nanosheets were found playing important roles in various applications[32]. The roles of different types of defects in MoS2 nanosheets in airborne Hg0 adsorption remain unexplored. Ab initio calculation was conducted to study mechanism of the adsorption of Hg0 on MoS2 nanosheets with different types of defects. Characterisation of defect-rich MoS2 containing materials was carried out, followed by the testing of the performance of this material in Hg0 adsorption
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