Theoretical Investigation of S, P, and O-Doping Effect on the Photocatalytic Efficiency of g-C3-N4 Monolayer

Graphitic carbon nitride (g-C 3 N 4 ) is a low-cost photocatalyst with high stability and many applications. However, photocatalytic activity of g-C 3 N 4 has been limited due to its low visible light absorption and high electron-hole pair recombination rate. In this study, the effect of P and O doping on the geometrical and electronic properties of the g-C 3 N 4 is investigated using density functional theory (DFT) calculations. The results showed that the surface area increased in the cases of the S- and P-doped systems. Electron density distribution of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular (LUMO), and natural bond orbital (NBO) analyses illustrated that, among the S- and O-doped systems, S int - and O int -doped g-C 3 N 4 structures had high delocalization. Delocalization of electrons increased after non-metal doping at the edge site. Phosphorus doping at the N edge site led to a stronger donor-acceptor interaction. The most stable configuration was related to doping at the edge (S- and O-doped) and corner carbon (P-doped) site. According to the results of Time-dependent density-functional theory (TD-DFT) calculations, the S ed - and P C -doped g-C 3 N 4 had more light harvesting ability and less overlap integral than g-C 3 N 4 quantum dots (QCNs) and O ed -doped CN had more light harvesting ability than QCNs. On the basis of the results, non-metal doping increased visible light-harvesting and lifetime of the e - -h + pair, which led to increased photocatalytic efficiency