Metal-doped graphitic carbon nitride (g-C₃N₄) as selective NO₂ sensors: a first-principles study

Abstract

In this research, the potential application of metal-doped g-C₃N₄ as highly sensitive molecule sensors for NO₂ detection was studied using density function theory (DFT) calculations. Various metal-doped (Ag-, Au-, Co-, Cr-, Cu-, Fe-, K-, Li-, Na-, Mn-, Pt-, Pd-, Ti-, V-) g-C₃N₄ sheets were considered. CO, CO₂, NH₃, N₂ and NO₂ molecules were found to adsorb on metal-doped g-C₃N₄ via strong chemical bonds. Chemisorbed gas molecules and metal-doped g-C₃N₄ formed charge transfer complexes with different charges transferring from metal-doped g-C₃N₄ to gas molecules. Pristine and metal-doped g-C₃N₄ sheets were demonstrated as potential capturers for certain gas molecules according to the adsorption energy, isosurface of electron density difference, and density of states analysis. Among the diverse metal-doped g-C₃N₄ sheets, Ag-, K-, Na-, and Li-doped g-C₃N₄ were found to be clearly sensitive to the NO₂ molecule. The adsorption energies between NO₂ and Ag-, K-, Na-, and Li-doped g-C₂N4 were significantly greater than those of the other gas molecules (CO, CO₂, N₂, and NH₃). The density of states indicates that the NO₂ adsorption on Ag-, K-, Na-, and Li-doped g-C₃N₄ induced the shift of the total density of state in the positive energy direction. Charge transfer results also demonstrate that chemical interactions existed between NO₂ and Ag-, K-, Na-, and Li-doped g-C₃N₄. All these results suggest the strong potential of Ag-, K-, Na-, and Li-doped g-C₃N₄ for application as highly sensitive molecule sensors.