Abstract
Elemental mercury has become a global concern because of its significant impact on human health and the ecosystem. A lot of effort has been put towards the removal of elemental mercury from the 2H-MoS2 (prismatic structure of MoS2). However, the mechanism of 1T-MoS2 (polytype structure of MoS2) in Hg0 capture remains unexplored. In this study, density functional theory (DFT) was adopted to investigate the adsorption mechanism of Hg on a 1T-MoS2 monolayer. The different possible adsorption positions on the 1T-MoS2 were examined. For different adsorption configurations, the changes in electronic property were also studied to understand the adsorption process. The results elucidated that chemisorption dominates the adsorption between Hg0 atoms and the 1T-MoS2. It was found that the TMo (on top of the Mo atom) position is the strongest adsorption configuration among all the possible adsorption positions. The adsorption of Hg0 atoms on the 1T-MoS2 monolayer is influenced by adjacent S and Mo atoms. The adsorbate Hg0 atom is found being oxidized on the TMo position of the 1T-MoS2 with an adsorption energy of −1.091 eV. From the partial density of states (PDOS) analysis of the atoms, the strong interaction between Hg0 and the 1T-MoS2 surface is caused by the significant overlap among the d orbitals of the mercury atom and the s orbital of the S atom and p and d orbitals of the Mo atom.
Highlights
Elemental mercury (Hg0) is the most toxic form of mercury in flue gas released from industrial activity (Galbreath and Zygarlicke, 1996; Presto and Granite, 2006)
Our previous research showed that MoS2 is an elemental Hg trapping agent with a trigonal prismatic (2H) structure (Zhao et al, 2016), wherein the layer of Mo atoms is sandwiched between two layers of S atoms, such that each Mo is coordinated to six S atoms in a trigonal prismatic geometry (Yin et al, 2011; Chhowalla et al, 2013)
Because the density functional theory (DFT)-D mainly focuses on the dispersion force between adsorbent and the adsorbate system, the adsorption behavior of a single Hg atom can be calculated more accurately
Summary
Elemental mercury (Hg0) is the most toxic form of mercury in flue gas released from industrial activity (Galbreath and Zygarlicke, 1996; Presto and Granite, 2006). Because it is insoluble in water, highly volatile, and chemically inert, it can be trans-. The 2H-MoS2, the most stable phase of a MoS2 monolayer, has been examined extensively for the adsorption of mercury on the defect-free to defective surface. Not much work has been carried out on the adsorption of mercury on the other geometric structure of MoS2, the polytype (1T) with a tetragonal symmetry, which has one MoS2 layer per repeat unit in the octahedral phase
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