Markedly different adsorption behaviors of gas molecules on defective monolayer MoS2: a first-principles study

Abstract

Sulfur vacancy (SV) is one of the most typical defects in two-dimensional monolayer MoS₂, leading to reactive sites. We presented a systematic study of the adsorption behaviors of gas molecules, CO₂, N₂, H₂O, CO, NH₃, NO, O₂, H₂ and NO₂, on monolayer MoS₂ with single SV by first-principles calculations. It was found that CO₂, N₂ and H₂O molecules physisorbed at the proximity of single SV. Our adsorption energy calculations and charge transfer analysis showed that the interactions between CO₂, N₂ and H₂O molecules and defective MoS₂ are stronger than the cases of CO₂, N₂ and H₂O molecules adsorbed on pristine MoS₂, respectively. The defective MoS₂ based gas sensors may be more sensitive to CO₂, N₂ and H₂O molecules than pristine MoS₂ based ones. CO, NO, O₂ and NH₃ molecules were found to chemisorb at the S vacancy site and thus modify the electronic properties of defective monolayer MoS₂. Magnetism was induced upon adsorption of NO molecules and the defective states induced by S vacancy can be completely removed upon adsorption of O₂ molecules, which may provide some helpful information for designing new MoS₂ based nanoelectronic devices in future. The H₂ and NO₂ molecules were found to dissociate at S vacancy. The dissociation of NO₂ molecules resulted in O atoms located at the S vacancy site and NO molecules physisorbed on O-doped MoS₂. The calculated results showed that NO₂ molecules can help heal the S vacancy of the MoS₂ monolayer.