Influence of B, Zn, and B-Zn doping on electronic structure and optical properties of g-C3N4 photocatalyst: A first-principles study

The electronic structures and optical properties of pure, B-doped, Zn-doped and B-Zn co-doped tri-s-triazine g-C3N4 were studied by using first-principles method. The results show that the band gaps of all doped g-C3N4 systems decrease relative to that of pure g-C3N4. The band gap of B-doped g-C3N4 is the smallest, 1.546 eV. The band gaps of Zn-doped and B-Zn co-doped g-C3N4 are very close, 2.047 eV and 2.100 eV, respectively. Although the absorption peaks of all doped g-C3N4 systems exhibit blue shift, and the strength of absorption peak of B-Zn co-doped g-C3N4 decreases relative to that of pure g-C3N4, the optical absorptions of doped g-C3N4 are enhanced in visible light range. When the wavelength is larger than 405 nm and less than 526 nm, the optical absorption of B-Zn co-doped g-C3N4 is enhanced, while the optical absorptions of all doped g-C3N4 systems are enhanced when the wavelength is larger than 526 nm. The optical absorption of B-Zn co-doped g-C3N4 is the strongest between 539 nm and 750 nm, then B- and Zn-doped g-C3N4 in order, while that of B-doped g-C3N4 is the strongest when the wavelength is larger than 750 nm, then B-Zn co-doped g-C3N4, and Zn-doped g-C3N4.