A comparative study of mechanisms of the adsorption of CO(2) confined within graphene–MoS(2) nanosheets: a DFT trend study

The space within the interlayer of 2-dimensional (2D) nanosheets provides new and intriguing confined environments for molecular interactions. However, atomic level understanding of the adsorption mechanism of CO(2) confined within the interlayer of 2D nanosheets is still limited. Herein, we present a comparative study of the adsorption mechanisms of CO(2) confined within graphene–molybdenum disulfide (MoS(2)) nanosheets using density functional theory (DFT). A comprehensive analysis of CO(2) adsorption energies (E(AE)) at various interlayer spacings of different multilayer structures comprising graphene/graphene (GrapheneB) and MoS(2)/MoS(2) (MoS(2)B) bilayers as well as graphene/MoS(2) (GMoS(2)) and MoS(2)/graphene (MoS(2)G) hybrids is performed to obtain the most stable adsorption configurations. It was found that 7.5 Å and 8.5 Å interlayer spacings are the most stable conformations for CO(2) adsorption on the bilayer and hybrid structures, respectively. Adsorption energies of the multilayer structures decreased in the following trend: MoS(2)B > GrapheneB > MoS(2)G > GMoS(2). By incorporating van der Waals (vdW) interactions between the CO(2) molecule and the surfaces, we find that CO(2) binds more strongly on these multilayer structures. Furthermore, there is a slight discrepancy in the binding energies of CO(2) adsorption on the heterostructures (GMoS(2), MoS(2)G) due to the modality of the atom arrangement (C–Mo–S–O and Mo–S–O–C) in both structures, indicating that conformational anisotropy determines to a certain degree its CO(2) adsorption energy. Meanwhile, Bader charge analysis shows that the interaction between CO(2) and these surfaces causes charge transfer and redistributions. By contrast, the density of states (DOS) plots show that CO(2) physisorption does not have a substantial effect on the electronic properties of graphene and MoS(2). In summary, the results obtained in this study could serve as useful guidance in the preparation of graphene–MoS(2) nanosheets for the improved adsorption efficiency of CO(2).