Adsorption properties of MoS2 monolayers modified with TM (Au, Ag, and Cu) on hazardous gases: A first-principles study

This study focused on investigating the adsorption and detection performance of intrinsic and Au, Ag, Cu doped monolayers of molybdenum disulfide (MoS2) for air pollutants (NO2, NH3, CH4, CO2, SO2, and SO3). By using first-principles density functional theory (DFT), calculations were performed on parameters related to structural properties, electronic properties, and adsorption properties. Besides, the possibility of applications was further explored by considering the work function (WF), optical absorption coefficient, thermodynamic stability, and desorption performance. Firstly, the adsorption energy (Eads) showed that the position of doped atoms (Au, Ag, and Cu) in the MoS2 substrate directly affects gas selectivity and improves the adsorption of gas molecules to different degrees. Obviously, when NO2 is adsorbed onto a substrate of Cu-substituted S-doped MoS2 (MoxS2x-1Cu), the Eads are observed to be 9.9 times higher than that of intrinsic MoS2. Moreover, the charge transfer of gas absorbed is enhanced after doping atoms, with a maximum increase of 6.9 times. Secondly, in doped adsorption gas systems, the WF increases by at least 27.3, along with a significant increase in the absorption coefficient in the visible light region. It is also indicated that the presence of doped atoms enhances the gas sensitivity of MoS2. According to the desorption time, MoxS2x-1Cu–NH3 and Mox-1AuS2x-SO3 can achieve rapid desorption after being artificially heated. The desorption time can be as fast as 10 s. This work is found to elucidate the gas adsorption mechanism of doped MoS2 materials, which provides a solid theoretical foundation for enhancing the detection capability of gas sensors using modified MoS2-sensitive materials.