Activation of MoS2 monolayers by substitutional copper and silver atoms embedded in sulfur vacancies: A theoretical study

Defective molybdenum disulfide monolayers, with up to three copper and silver atoms substituting sulfur atoms, were studied at a dispersion-corrected DFT level. By the first time, changes produced on electronic properties, reactivity, charge distribution and electrostatic potential by trapping these atoms are widely discussed. Embedded species are expected to remain stable and fixed, since large and favorable metal cluster-vacancy defective monolayer binding energies are obtained, higher than - 2.60 eV in all cases. Several defect states are induced in the forbidden region, being the band gap reduced as more substitutional atoms are added. These states mostly come from molybdenum d and p orbitals from embedded metals. Also, defects reduce the gap up to 0.10 and 0.35 eV, for copper and silver trimers, respectively. Substitutional single atoms and dimers donate charge to molybdenum atoms in the middle layer, whereas trimers tend to accumulate it. However, charge transfer is marginal and the most important rearrangements are produced in atoms neighboring defects. Regions with lower electrostatic potential are produced around the defects. Condensed Fukui indices reveal that systems with defects enhanced the chemical reactivity, towards nucleophilic and nucleophilic attacks, in regions around the embedded species. In contrast to the chemically inert pristine MoS2 monolayer, changes on electronic, energetic properties and reactivity of all defective systems indicate that are promising materials for catalytic purposes and to adsorb other molecules.