Monolayer Sc2CF2 as a Potential Selective and Sensitive NO2Sensor: Insight from First-Principles Calculations

Abstract

Two-dimensional materials with excellent surface-volume ratios and massive reaction sites recently have been receiving attention for gas sensing. With first-principles calculations, we explored the performance of monolayer Sc2CF2as a gas sensor. We investigated how molecule adsorption affects its electronic structure and optical properties. It is found that a large charge transfer quantity happens between Sc2CF2and NO2, which results from the fact that the lowest unoccupied molecular orbital (LUMO) of NO2is below the valence band maximum (VBM) of Sc2CF2. Moreover, the MD simulation shows that NO2can adsorb on the Sc2CF2surface stably at room temperature. We explored the effect of biaxial strain on the adsorption energy and charge transfer quantity of each system, and the results show that the biaxial strain can enhance both the adsorption energy and charge transfer quantity of the NO2system and thus can improve the sensitivity of Sc2CF2in detecting the NO2molecule. Furthermore, we investigated the adsorption behavior and charge transfer of polar polyatomic molecules at the Sc2CF2surface with h-BN as a substrate, and the results demonstrate that the h-BN substrate can hardly modify the main results. Our result predicts that Sc2CF2can be a promising selective and sensitive sensor to detect the NO2molecule, and could also give a theoretical guide for other terminated MXenes used for gas sensors or detectors.