Stability of defects in monolayer MoS 2 and their interaction with O 2 molecule: A first-principles study

The stability of various defects in monolayer MoS2, as well as their interactions with free O2 molecules were investigated by density functional theory (DFT) calculations coupled with the nudged elastic band (NEB) method. The defects including S vacancy (monosulfur and disulfue vacancies), antisite defect (MoS) and external Mo atom can exist steadily in monolayer MoS2, and introduce defect levels in these defective systems, which breaks the surface chemical inertness and significantly enhances the adsorption capacity for free O2. The adsorption energy calculations and electronic properties analysis suggest that there is a strong interaction between O2 molecule and defective system. The adsorbed O2 on the defective surface can dissociate with a lower activation energy barrier, which produce two active oxygen atoms. Especially, two Mo atoms can occupy one Mo lattice site, and adsorbed O2 on the top of the Mo atom can then dissociate directly with the lowest activation energy barrier. Hence, our work may provide useful information to design MoS2-based gas sensor or catalysts.