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 .