▎ 摘　　要

The adsorption performance of ten gas molecules (H-2, N-2, O-2, CO, CO2, H2O, NO, NO2, SO2 and CH4) on graphene/WSe2 heterostructure is studied by means of first-principles calculations. The results show that gas molecules are physisorbed on the heterostructure surface owing to the weak interface interaction between gas molecules and graphene/WSe2. Meanwhile, NO2 has the strongest interactions with the graphene/WSe2 heterostructure among these gas molecules, suggesting the heterostructure has the highest selectivity towards NO2. Moreover, NO2 behaves as an electron acceptor and attracts electrons from graphene/WSe2 heterostructure, resulting in the reduction of Schottky barrier height of the heterostructure. Further, the controlled external electric field regulates the adsorption properties of the gas-graphene/WSe2 system in terms of the adsorption energies, band structures, and charge transfer. It is found that the sensitivity of NO2 on graphene/WSe2 heterostructure can be enhanced under large positive electric field (E = +0.5 V/angstrom), which induced by the charge redistribution between gas and the heterostructure. Our work will provide a preference to design the WSe2-based sensors with high sensitivity and selectivity.