Monolayer Janus Te2Se-based gas sensor to detect SO2 and NOx: a first-principles study

Abstract

In this study, the adsorption of gas molecules, such as O₂, NH₃, CO, CO₂, H₂O, NO_x (x = 1, 2) and SO₂, on Janus Te₂Se monolayer has been investigated by means of density functional theory (DFT) calculations. We show that Janus Te₂Se monolayer is preferable for SO₂ and NO_x molecules with suitable adsorption strength and apparent charge transfers. We further calculated the current–voltage (I–V) curves using the nonequilibrium Green's function (NEGF) method. The transport feature exhibits distinct responses with a dramatic change of I–V curves before and after NO_x (SO₂) adsorption on Janus Te₂Se. Thus, we predict that Janus Te₂Se could be a promising candidate for SO₂ and NO_x sensors with high selectivity and sensitivity. Moreover, the effect of strain on the gas/substrate adsorption systems was also studied, implying that the strained Janus Te₂Se monolayer could enhance the sensitivity and selectivity to SO₂ and NO₂. The adsorbed SO₂ and NO₂ on Janus Te₂Se could escape by releasing the applied strain, which indicates that the capture process is reversible. Our study widens the application of Janus Te₂Se not only as piezoelectric materials, but also as a potential gas sensor or capturer of SO₂ and NO_x with high sensitivity and selectivity.