1T′-MoS₂, A Promising Candidate for Sensing NO_x

Recently, ultrathin MoS₂ sheets in the semiconducting 2H phase have been fabricated into high-performance gas sensors. Here, we investigated the gas-sensing behavior of MoS₂ in the metallic 1T′ phase via first-principles calculations. We found that monolayered and few-layered 1T′-MoS₂ exhibit high selectivity and sensitivity toward NO molecules. Moreover, the adsorption of NO and NO₂ molecules on monolayered and few-layered 1T′-MoS₂ can be significantly strengthened by tensile strain, whereas the adsorption of other common gas molecules (e.g., CO, CO₂, NH₃, SO₂) is strain-insensitive. This distinct behavior suggests that high selectivity of NO_x over other gases on 1T′-MoS₂ can be achieved through strain engineering. In addition, the 50% S-passivated Mo-edges of 1T′-MoS₂ are found to be more active than the basal plane. Our results suggest that monolayered and few-layered 1T′-MoS₂ sheets (both basal plane and edges) are promising gas-sensing materials.