First-principles study of electronic and optical properties of NH3-adsorbed Sc2CO2 monolayer and its application in gas sensors

Two-dimensional Sc2CO2 MXene materials have been considered highly potential for gas capture and gas sensor applications. In this study, the adsorption behaviors of small molecules such as NH3, SO3, O2, H2CO and C2H4 on Sc2CO2 monolayer were investigated using first-principles methods. Our results demonstrate the preferential adsorption of NH3 over other species with adsorption energies as high as −0.55 eV. And Sc2CO2 is transformed from an indirect bandgap semiconductor to a direct bandgap semiconductor after NH3 adsorption, and the appropriate band gap makes it potential for light absorption and photodetection. In addition, the carrier mobility of Sc2CO2 monolayer is significantly enhanced by adsorption, making it easy to detect changes in resistance. The room-temperature electron mobilities of NH3-adsorbed Sc2CO2 along armchair and zigzag directions are predicted to be as high as 16.75 × 103 and 13.19 × 103 cm2V−1S−1, while the room-temperature hole mobilities along armchair and zigzag directions are determined to be 10.77 × 103 and 11.09 × 103 cm2V−1S−1, respectively. According to the present results, Sc2CO2 monolayer is expected to be promising for the design and application of efficient NH3 gas sensor devices with high selectivity, high sensitivity and low recovery time through analytical methods based on optical and/or electronic responses.