Highly Sensitive Gas Sensors Based on Ag-Doped SnS Monolayer for NO2 and NO Harmful Gases Detection

In the post-epidemic era, with the rapid recovery of industry and the massive use of chemical energy, excess toxic and harmful gases, such as nitrogen dioxide (NO2) and nitric oxide (NO), are emitted into the atmosphere. The development of NO2 and NO gas sensors with excellent gas sensing capabilities can provide a basis for online monitoring of toxic and harmful gases. Based on the first principles calculation of density functional theory (DFT), first, the doping structure of a single Ag atom on the stannous sulfide (SnS) monolayer surface was optimized, and the binding energy ((Eb) was calculated to obtain the optimal doping structure. Then, ten kinds of gas molecules (NO2, NO, C2H2, hydrogen sulfide (H2S), carbon monoxide (CO), SOF2, SO2, H2, CH4, and CO $_{{2}})$ were close to the Ag–SnS monolayer in different ways. The adsorption structure, adsorption energy ( ${E}_{\text {ads}})$ , and charge transfer amount ( $\Delta {Q})$ of the above gas molecules on the surface of the Ag–SnS monolayer were calculated and analyzed. Finally, the total density of states (TDOS) and energy band structure of the system before and after gas adsorption were compared and analyzed to explore the interaction mechanism between each gas molecule and the Ag–SnS monolayer. It is found that the Ag–SnS monolayer has good adsorption properties for NO2 and NO gas molecules and both are chemical adsorptions. Therefore, the gas sensor based on Ag–SnS monolayer has a good application prospect in the field of toxic and harmful gases.