Adsorption and dissociation of mercury species on the surface of 1T-MnO2/graphene

Abstract

In this paper, the adsorption of HgCl and HgO mercury species is studied on the 1T-MnO2/graphene heterostructure, using the Density Functional Theory (DFT) within the framework of Generalized Gradient Approximation of Perdew-Burke and Ernzerhof (GGA-PBE) along with atomic pseudopotentials. The heterostructure is modelled using the periodic slab scheme, with a vacuum region of 26 Å. In this investigation, the surface of interest is the monolayer of 1T-MnO2 coupled to a monolayer of graphene and its interaction with the HgCl and HgO species of mercury. The graphene monolayer only acts as a substrate to support the 1T-MnO2 monolayer; for that reason, in all of the processes of adsorption of the HgCl and HgO species of mercury onto the heterostructure, the atomic positions of the graphene remain fixed.In order to study the most energetically favorable adsorption model, the especial sites TO1, TO2, TM1 and TM2 in the 1T-MnO2/graphene surface are considered as well as the different orientations of the HgCl and HgO molecules on the heterostructure surface. In both cases, it is concluded that the most energetically favorable site is TO2 with adsorption energy values of −1.668 eV and −1.904 eV respectively. The analysis of the possible molecular dissociation scenarios shows that the HgCl and HgO species are strongly adsorbed (chemically) by the surface of the heterostructure. In particular, after of the adsorption process, the HgO molecule is dissociated by the 1T-MnO2/graphene heterostructure, where the oxygen atom is removed, and the mercury atom is adsorbed by the surface of the heterostructure. This scenario is highest favorable for the adsorption of Hg on the heterostructure. These results obtained indicate that the heterostructure behaves as a formidable substrate for the capture of the HgCl and HgO species. Lastly, the effect of their adsorption over the surface of the 1T-MnO2/graphene heterostructure in terms of electronic properties is analyzed for the most energetically stable configurations in each case.