  First-principles calculations within density functional theory (DFT) have
been carried out to investigate the adsorption of various gas molecules
including CO, CO2, NH3, NO and NO2 on MoS2 monolayer in order to fully exploit
the gas sensing capabilities of MoS2. By including van der Waals (vdW)
interactions between gas molecules and MoS2, we find that only NO and NO2 can
bind strongly to MoS2 sheet with large adsorption energies, which is in line
with experimental observations. The charge transfer and the variation of
electronic structures are discussed in view of the density of states and
molecular orbitals of the gas molecules. Our results thus provide a theoretical
basis for the potential applications of MoS2 monolayer in gas sensing and give
an explanation for recent experimental findings.
