Adsorption of CO2, CO, NH3, NO2 and NO on g-C3N5 surface by first-principles calculations

Inspired by recent successfully experimental approach of a new graphitic C3N5 (termed as g-C3N5) material, the absorption of small gas molecules, including CO2, CO, NH3, NO2 and NO, on g-C3N5 surface is theoretically investigated by density functional theory calculations. The adsorption energy between g-C3N5 and NO is lower than those of the other gas molecules. The band structures display that the band gaps of NH3, CO, CO2, and NO2 adsorption system are 0.63, 0.58, 0.52 and 0.11 eV, respectively, compared to g-C3N5 (0.53 eV). When NO is adsorbed, the band structure shows that the valence band covers Fermi level but there is still a small band gap near Fermi level, revealing that hole doping exists and NO adsorption system has p-type conductivity. Charge difference density distribution reveals that the adsorption progress helps NO to lose electrons and g-C3N5 to gain electrons. Thus, compared to other gas molecules, the lowest adsorption energy and p-type conductivity in NO adsorption system indicate that g-C3N5 may provide a good adsorption surface to detect NO molecule.