First-Principles Study of Sc, B Doped g-C3N4/TiO2 Heterojunctions for Enhanced Photocatalytic Performance

The crystal structure, electronic properties, and photocatalytic performance of g-C3N4/TiO2 heterojunctions, as well as g-C3N4/TiO2 heterojunctions doped with Sc and B individually and simultaneously, were investigated using first-principles calculations based on density functional theory. The results show that both TiO2 and g-C3N4 crystals exhibit good structural stability. The interaction between a single layer of g-C3N4 and the TiO2 (101) surface forms a van der Waals heterojunction, which has the advantages of a narrow bandgap, a wide spectral response range, and high carrier migration efficiency. This heterojunction can effectively address the issue of high energy consumption in the degradation of organic pollutants. The heterojunction models before and after doping are reasonable and feasible. The bandgap is narrowed, which can effectively suppress the recombination of photo-generated electron-hole pairs. The band structure of the staggered two-crystal heterojunction promotes charge separation and carrier migration. Doping with Sc and B introduces hybrid states, which not only adjust the redox ability but also further reduce the bandgap. Among them, the effect of simultaneous doping is the most significant, with a bandgap of 2.178 eV. This accelerates charge transfer, shifts the light absorption edge to the red side, increases the response range in the visible light region, enhances light absorption performance, and exhibits better photocatalytic performance.