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

Highlights: • The adsorption energies of CO₂, CO, NH₃, NO₂ and NO on g-C₃N₅ are all negative. • The adsorption energy between g-C₃N₅ and NO is lowest. • When NO is adsorbed on g-C₃N₅, the system has p-type conductivity. 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.