First-Principles Study on Bi<sub>2</sub>Te<sub>2</sub>S Monolayer for Adsorption Performance and Sensing Capability

In\nthis study, a comprehensive investigation into the gas sensing\ncapabilities of the two-dimensional (2D) Bi<sub>2</sub>Te<sub>2</sub>S was conducted using first-principles calculations based on density\nfunctional theory. A wide array of gas molecules, including CH<sub>4</sub>, Cl<sub>2</sub>, CO, CO<sub>2</sub>, H<sub>2</sub>, H<sub>2</sub>O, H<sub>2</sub>S, N<sub>2</sub>, NH<sub>3</sub>, NO, NO<sub>2</sub>, O<sub>2</sub>, and SO<sub>2</sub>, was encompassed in this\nwork. Through the strategic placement of these gas molecules at different\nlocations on the Bi<sub>2</sub>Te<sub>2</sub>S monolayer and taking\ninto account a range of configurations, the adsorption process was\nthoroughly investigated, with a particular emphasis on the structures\nthat are most thermodynamically stable. It was revealed that Cl<sub>2</sub>, O<sub>2</sub>, NO, and NO<sub>2</sub> molecules exhibit\na pronounced affinity for the Bi<sub>2</sub>Te<sub>2</sub>S monolayer.\nNotably, it was found that the Cl<sub>2</sub>@Bi<sub>2</sub>Te<sub>2</sub>S, O<sub>2</sub>@Bi<sub>2</sub>Te<sub>2</sub>S, and NO<sub>2</sub>@Bi<sub>2</sub>Te<sub>2</sub>S systems’ gas adsorption\ncapabilities are greatly enhanced by the introduction of an external\nelectric field. Moreover, the addition of horizontal biaxial strain\nsignificantly impacts the gas adsorption properties of the O<sub>2</sub>@Bi<sub>2</sub>Te<sub>2</sub>S system, underscoring the tunability\nof the Bi<sub>2</sub>Te<sub>2</sub>S monolayer’s sensing capabilities.\nIn light of these theoretical results, the Bi<sub>2</sub>Te<sub>2</sub>S monolayer is proposed to have great potential as an extremely sensitive\nand selective gas sensing material, especially for identifying Cl<sub>2</sub>, O<sub>2</sub>, NO, and NO<sub>2</sub>. This study clarifies\nthe intrinsic gas sensing capabilities of the Bi<sub>2</sub>Te<sub>2</sub>S monolayer, while highlighting how its performance can be\ntailored in response to external stimuli, setting the stage for the\nadvancement of more sophisticated gas sensing devices.