First-Principles Exploration of the Electronic Structure and Optical Properties of S-Doped Bi4O5Br2

At present, many research studies have explored the modification of Bi4O5Br2, but relatively few have focused on non-metallic doping. In particular, the effect of S doping on its photocatalytic mechanism remains unclear. Hence, this study systematically investigates the modulation mechanism of the electronic structure and optical properties of Bi4O5Br2 by doped S using density functional theory (DFT) calculations. The calculated results indicate that the Br4Br1 model, in which S replaces Br at sites 4 and 1, is the most thermodynamically stable configuration. Comparing the models before and after doping, it is found that S doping significantly alters the lattice parameters of Bi4O5Br2, thus affecting its electronic structure. Furthermore, differential charge density calculations reveal that S doping improves the charge transfer capability and enhances the separation efficiency of photogenerated electron–hole pairs in Bi4O5Br2. Calculated absorption spectra demonstrate that S doping augments the light absorption of Bi4O5Br2 in the low- and medium-energy regions. Moreover, the dielectric function calculations further validate the effect of S doping on the optical properties of Bi4O5Br2. Specifically, there is an increase in polarization and energy loss in the low-energy region, with the opposite trend in the middle- and high-energy regions. Overall, S doping elevated the light absorption capacity and charge transfer efficiency of Bi4O5Br2 by altering its lattice parameter and electronic structure, which facilitated the enhancement of photocatalytic performance. This study provides new insights into the development of efficient photocatalytic materials and broadens the potential of Bi4O5Br2 for photocatalytic applications.