Unveiling the gas sensing potential of CxNy monolayer through ab initio screening

Abstract

The development of superior performance and safety metal free sensors for harmful gas detection is of great significance, but it is still challenging. In this study, we developed a new strategy denoted as ‘5S’ (stability, sensitivity, selectivity, speed recovery time and safety) to screen CxNy (x:2∼5, y:1∼8) monolayer as outstanding performance gas sensors (NO, NO2, NH3, CO and CO2) via density functional theory (DFT). The results indicate that all gas molecules are adsorbed on the CxNy surface due to the negative adsorption energy; interestingly, the electron transfer changes slightly during the interaction between CxNy and the adsorbed gas molecules. The adsorption energy of C2N, C3N4, C3N5, C5N8 for NO2 hazardous gas is particularly pronounced and difficult to desorb from CxNy compared to the other candidate CxNy, which suggests that it hinders to be a promising gas sensor. Conversely, the adsorption energies of C2N and C5N8 for small gas molecules are too small, resulting in insufficient sensibility. It is worth noting that C3N4, C3N5 is a potential candidate substrate for NO due to its optimized adsorption/desorption properties and fast recovery time. Furthermore, C3N4 can be used as a gas sensor for NH3 due to its suitable adsorption/desorption properties and fast recovery time compared to other substrates. This work not only theoretically screens C3N5 and C3N4 substrates for excellent performance as gas sensors, but also provides a new ‘5S’ screening strategy for other 2D materials as candidates for gas sensors.