| dc.description.abstract | Graphitic carbon nitride, recognized for its intermediate band gap of approximately 2.7 eV and exceptional chemical and thermal stability, has emerged as a prominent candidate in environmental photocatalysis. Nonetheless, its effectiveness remains suboptimal due to limited absorption of visible light, inadequate surface area, poor electronic conductivity, and high recombination rates of photogenerated electron-hole pairs. To address these shortcomings and enhance photocatalytic efficiency, modifying g-C3N4 is imperative. Among the various strategies for modification, element doping stands out as an efficient and straightforward method for adjustment the electronic structure and promoting photocatalytic performance. This study utilizes density functional theory (DFT) calculations to investigate how non-metal doping (B, P), metal doping (Na, K), and co-doping (Na+B, Na+P, K+B, K+P) affect the optical properties of g-C3N4. Various analysis methods were employed, including the GW plus Bethe-Salpeter equation (GW-BSE) method, density of states (DOS) analysis, bandstructure analysis, Bader charge, effective mass, as well as analysis of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Their visible light absorption spectra were obtained, revealing varying degrees of broadened visible light absorption ranges and increased visible light absorption intensities across all doping methods. The band structure indicates a reduction in band gap depending on the doping element introduced. A significant decrease was observed in the case of Na+B co-doping, at which the band gap decreased from 2.7 to 0.15 eV. This substantial reduction contributes to a notable enhancement in the visible light absorption spectrum compared to g-C3N4. Additionally, the analysis of HOMO and LUMO indicates that element doping can increase orbital hybridization and delocalization. Effective mass analysis also shows that doping can effectively reduce the high hole effective mass of pristine g-C3N4. These results suggest that elements doped is beneficial for improving carrier mobility and reducing the recombination rate. This study demonstrates the efficacy of various doping strategies, in enhancing the photocatalytic performance of g-C3N4 and provides insights into the electronic structure modifications induced by doping. | en_US |