Theoretical investigation on gas sensing characteristics of 3d transition metal atom doped C9N7 for toxic gases (CO, NO, NO2, and SO2)

This study investigates the sensing performance of a series of 3d transition metal doped C9N7 sensor structures for four toxic gases (CO, NO, NO2, and SO2). A series of sensor configurations with single and double 3d transition metal atoms doped with C9N7 (TM-C9N7 and TM2-C9N7) are constructed. The stability of the sensor configuration is evaluated by calculating the formation energy and dissolution potential. The stability analysis results indicate that except Sc-C9N7, Mn2-C9N7, and Cr2-C9N7, all sensor configurations have good structural stability. For screened sensor structures with good structural stability, the adsorption energy values of four toxic gases and three common gases (N2, O2, and CO2) are compared to evaluate their selectivity towards toxic gases. Moreover, the recovery times are also calculated to further evaluate the sensing performance. Through comprehensive evaluation, four sensor structures (Fe-C9N7, Cu-C9N7, Zn-C9N7, and Zn2-C9N7) with high selectivity and relatively short recovery time for toxic gases are determined. Among them, Fe-C9N7 is suitable for sensors of toxic gases NO2, and SO2, while Cu-C9N7, Zn-C9N7, and Zn2-C9N7 have good sensing performance for all four toxic gases.