Oxygen and Nitrogen Vacancies in a BiOBr/g-C₃N₄ Heterojunction for Sustainable Solar Ammonia Fertilizer Synthesis

Efficient and economical nitrogen fixation photocatalysts are one of the most attractive goals in ammonia-demanding agricultural production. Herein, a straightforward defect engineering and heterojunction strategy has been presented. Using in situ solvothermal techniques, a BiOBr/g-C3N4 photocatalyst with oxygen and nitrogen double vacancies was achieved, and its NH3 yields exceeded that of g-C3N4 with a single N-vacancy and BiOBr with an O-vacancy by 23.5 and 2.9 times, respectively. Meanwhile, efficient spatial photocarrier separation was obtained through double vacancies and the interfacial interaction between the g-C3N4 and BiOBr. Additionally, BiOBr/g-C3N4/polyacrylonitrile (PAN) microfibers and related waterwheel-like reactors were designed. Upon natural sunlight, these can conduct long-term nitrogen fixation using only air and water. Compared with the BiOBr/g-C3N4 powder catalysts, BiOBr/g-C3N4/PAN microfiber catalysts exhibited higher stability and recoverability. The solar ammonia fertilizer produced by BiOBr/g-C3N4 supplies crops with essential nutrients, which foster their growth. This has significant implications for reducing the expenses associated with conventional nitrogen fertilizers and contributing to environmental preservation.