Unveiling the adsorption properties of 3d, 4d, and 5d metal adatoms on the MoS2 monolayer: A DFT-D3 investigation

The adsorption of metal (M) adatoms on two-dimensional (2D) transition-metal dichalcogenides (TMDs) monolayers have been used to tune the physical-chemical properties of 2D TMDs such as MoS2, however, our atomistic understanding of the binding mechanism, site preference, charge transfer, diffusion barriers, etc., of metal adatoms on MoS2 is far from satisfactory. Thus, we report spin-polarized density functional theory calculations within the D3 van der Waals (vdW) correction to characterize the adsorption properties of 15 metal adatoms (3d, 4d, 5d) on MoS2 at low-coverage limit. All adatoms can be separated into two groups, namely, Fe, Co, Ni, Ru, Rh, Os, Ir, and Pt bind covalently to the MoS2 monolayer on the top(Mo) site, where the binding mechanism can be explained by the combination of two factors, namely, (i) distortions within the MoS2 monolayers, which breaks the degeneracy of the electronic states and reduces their magnitude near the valence band maximum, and (ii) strong hybridization between the partially unoccupied d- and Mo d(z)(2)-states. In contrast, Pd has a strong preference for the hollow site compared with the top(Mo) site, however, Cu, Zn, Ag, Cd, and Hg adatoms bind to the top(Mo) and hollow sites with nearly the same energy (differences less than 0.10eV) due to the weak hybridization of the fully occupied metal d-states, while Au binds preferentially on the top(s) site. Thus, the M-MoS2 interactions are dominated by covalent and van der Waals interactions, which shows strong and weak dependence on the adsorption site preference, respectively.