S-Scheme In₂O₃ Nanoparticle/BiOBr Nanoplate Heterojunctions for Improved Photocatalytic Dye Degradation and Cr(VI) Reduction

The In2O3 nanoparticles were homogeneously attached on the BiOBr nanoplate surface to obtain S-scheme In2O3/BiOBr heterojunction photocatalysts by a hydrothermal route. The purity, crystal structure, chemical state, morphology, light absorption property, and photogenerated charge behavior of composites were investigated by XRD, SEM, TEM, HRTEM, XPS, UV–vis DRS, PL, ESR, and electrochemical tests. The removal of dyes (acid orange 7 (AO7), acid orange 10 (AO10), and rhodamine B (RhB)) and Cr(VI) was employed to evaluate the photocatalytic performance of In2O3/BiOBr composites irradiated by simulated sunlight. The results indicate that the photocatalytic performance of BiOBr can be remarkably promoted after the decoration of In2O3 nanoparticles, and the best photocatalytic activity was achieved over an 8% In2O3/BiOBr sample. The 8% In2O3/BiOBr sample also indicates outstanding synergistic photocatalytic performance for the removal of the heavy metal ion/dye mixture (AO7/Cr(VI) and RhB/Cr(VI)). It is found that the decoration of In2O3 nanoparticles can accelerate the transfer and separation of photoinduced electrons and holes in BiOBr nanoplates. The energy band structure, work function, and Fermi level of BiOBr and In2O3 were computed through the density functional theory calculation. Based on the above investigation, the photocatalytic mechanism of the S-scheme In2O3/BiOBr composite was discussed.