Computational study of the intercalation of NO2 between bilayer MoTe2

Transition-metal dichalcogenide (TMD) layers have been a subject of widespread interest as chemical sensors with their sensitivity selectively enhanced depending on the number of layers. The effect has been linked to possible intercalation of species such as nitrogen dioxide (NO2). However, whether intercalation helps or even occurs remains speculative. Hence, this work investigates, employing density functional theory (DFT) calculations, the intercalation of NO2 between bilayers of molybdenum ditelluride (MoTe2), its energy, and the impact on charge transfer. The effects are confronted with the intercalation of nitrogen molecules (N2) and the equivalent adsorption of both species. The results show that the intercalation of NO2 can be energetically favorable for <0.4, 1.5–3.0, and >4.0 × 10^14 molecules/cm2 and that at low coverage, the molecule-sheet interactions are too weak to facilitate sufficient interlayer expansion, and thus the molecules dissociate. The dissociation and non-dissociative intercalation of NO2 enhance the per molecule charge transfer by 1110% and 256%, respectively, relative to adsorption. Hence, in all favorable cases, the intercalation should significantly enhance the response of the system. Furthermore, the results suggest that the evacuation of NO2 should be feasible, allowing MoTe2 recovery. In contrast, N2 intercalation is unfavorable, illustrating the selectivity of the process.