Selective and sensitive toxic gas-sensing mechanism in a 2D Janus MoSSe monolayer

With an inspiration of sensing toxic gases, this study is aimed at exploring the potential of a Janus MoSSe monolayer as a gas sensor. Here, we focused on the adsorption mechanism after the exposure to NH₃, NO₂, NO, HCN, CO₂, CO, H₂, H₂S and SO₂ on both the S and Se sites of MoSSe. We investigated the structural geometries and electronic, sensing and electron-transport properties before and after adsorption of the aforementioned gases by applying DFT calculations. The results revealed the higher binding strength of NO₂/SO₂ and NO on Se and S sites, respectively, among all the gas adsorptions on the MoSSe monolayer. Moreover, DOS revealed strong orbital contributions at E_F, which confirmed the n/p-type semiconducting character for the NO/NO₂ adsorbed MoSSe monolayer. Further, the specific work function alteration after the adsorption of NO₂, SO₂ and NO indicated that the MoSSe monolayer could be a potential candidate for Φ-type gas sensor at 300 K. Additionally, the higher electron transmission and prominent electrical response values of 76.4/56 μA and 82 μA suggested a maximum sensitivity of 98%/89% and 93% at a particular voltage for NO₂/SO₂ and NO on Se and S sites, respectively. Thus, our results promote surface selectivity, i.e. S or Se site, and better sensitivity with recycling potential could enable sensing application of the Janus MoSSe monolayer for toxic gases detection.