Selective sensing of NH3 and NO2 on WSe2 monolayers based on defect concentration regulation

Defect engineering is an important method to control material properties. In this paper, large-scale sampling density functional theory (DFT) was used to investigate the adsorption and sensing behavior of NH3 and NO2 on a WSe2 monolayer, with a focus on the effect of selenium vacancy concentration. The results demonstrate that selectivity is inhibited on a perfect monolayer due to the similar adsorption energy of the two gases, NH3 and NO2, while selectivity can be obtained for both of them under different selenium vacancy concentrations (NH3 about 2-5.6%, NO2 about >8.3%). It is believed that the good match between the unique surface structure of the double-color (double-charged) wave wheel disk-like structure of the WSe2 monolayer and the molecular structure of both of the two representative molecules, NH3 and NO2, contributes dominantly to the unusual performance. The results demonstrate that one kind of material-WSe2 monolayer-can perform selective sensing of both NH3 and NO2, respectively, using only defect adjustment. It is particularly important to acquire the selectivity to NH3 in the mixture of NO2 and NH3. It also provides opportunities for understanding materials and patterned catalyst design.