CTAB-Induced Oxygen Vacancies and Z-Scheme Heterojunctions in Bi4O5Br2/BiOBr Ultrathin Nanosheets for Enhanced Photocatalytic Nitrogen Fixation

Bi-based oxyhalides have emerged as promising candidates for photocatalytic nitrogen fixation, yet their practical application remains constrained. In this study, ultrathin Bi4O5Br2/BiOBr Z-scheme heterojunctions were successfully fabricated via an in situ phase transformation. By introducing CTAB as a structural modifier, oxygen vacancies (OVs) were generated on the surface, while the additive simultaneously promoted the crystallization of 2D nanosheets and stabilized the heterojunction architecture. The Z-scheme mechanism effectively spatially separates photogenerated electrons and holes, while the oxygen vacancies enhance visible-light absorption and serve as active centers for nitrogen adsorption and activation. The optimized CTAB-assisted Bi4O5Br2/BiOBr photocatalyst achieved an ammonia production rate of 3489.6 μmol·gcat–1·L–1·h–1, representing a 2- and 1.24-fold enhancement over pristine Bi4O5Br2 and the unmodified heterojunction, respectively. This work provides a dual-functional strategy integrating defect engineering and heterostructure design to advance sustainable solar-driven nitrogen fixation.