Electronic and optical properties of metal decorated graphitic carbon nitride M/g-C3N4 (M = K, Ca, Ga, Ni, Cu): A theoretical study

Abstract

The influence of single metal doping (K, Ca, Ga, Ni, Cu) on the electronic and optical characteristics of graphitic carbon nitride (g-C3N4) was explored utilizing a semi-empirical tight-binding-based quantum chemistry technique (GFN2-xTB). The calculated results of interaction energy, analyzing the charge transfer, and the bond order revealed that chemical bonds were formed between the metal atom and g-C3N4. Furthermore, the bond formation between doped metal atoms with g-C3N4 is predominantly covalent, except for K. The fractional occupation density analysis of the M/g-C3N4 systems shows different distributions of active electrons across the material systems. The frontier molecular orbitals (HOMO, LUMO) distribution utilized to assess the photogenerated electron and hole recombination of the catalytic systems. Due to the efficient separation of the photogenerated electron-hole pairs, Ni/g-C3N4 exhibits the highest photocatalytic activity among the studied systems. On the basis of more extensive electronic and optical property calculations including ionization potential, electron affinity, global electrophilicity index, band gap energy, and UV-VIS spectra, the Ni/g-C3N4 photocatalyst's high activity can be explained and interpreted.