First-principles study of highly sensitive and selective gas-sensing properties of the C3N2 monolayers towards SO2 gas

Motivated by the design of efficient two-dimensional material-based gas sensors for SO2 gas detection, the geometrics, energetics, charge transfer, work function, electronic and sensing properties of C3N2 monolayers towards gases like SO2, H2S, CH4, C2H4, C2H6, CO, CO2, H2, N2, AsH3, NH3, PH3, N2O, H2O, NO, NO2, and O2 were investigated using first-principles calculations. Among the considered gases, only SO2 is chemisorbed on the C3N2 monolayer with remarkably adsorption energy (-1.001 eV) and charge transfer (-0.151 e). The adsorption of SO2 gas can effectively modify electronic properties of the C3N2 such as the change of band gap from 2.006 to 1.775 eV. The C3N2 monolayer toward SO2 gas has high sensitivity (over 96%) and selectivity. Although the recovery time of the monolayer toward SO2 is quite long (1.8 h) at 300 K, it is very rapid (4.1 s) at high temperature (350∼400 K), which is suitable for the C3N2 sensor to capture and desorb SO2 gas. These results indicate that the C3N2 sensor would be a good potential of highly sensitive and selective, reusable gas sensors for SO2 gas detection at 350∼400 K.