Synergistic enhancement of photocatalytic activity of Bi4O5Br2via cobalt doping and oxygen vacancy engineering

A series of cobalt-doped Bi₄O₅Br₂ (x% Co–BOB) materials with oxygen vacancies were synthesized via a hydrothermal method, where x represents the mass percentage of cobalt doping. Characterization by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) confirmed the successful incorporation of cobalt ions and revealed the materials’ structural features. Results demonstrate that the synergistic regulation of Co doping and oxygen vacancies (OVs) effectively optimized the band structure of Bi₄O₅Br₂, extending its light response range to the visible region, enhancing the separation rate of photogenerated carriers in Bi₄O₅Br₂ and significantly improving its photocatalytic performance. The degradation experiments demonstrated that the 3.5% Co–BOB sample exhibits the optimal photocatalytic activity. Under light irradiation, the 3.5% Co–BOB achieved 96% methylene blue (MB) degradation within 60 minutes, with a reaction rate constant 5.8 times that of undoped Bi₄O₅Br₂. Furthermore, the catalyst maintained excellent activity and structural stability over four consecutive cycles. This study not only provides a novel, high-efficiency photocatalyst for organic dye wastewater treatment but also offers valuable theoretical insights into enhancing photocatalyst performance through metal ion doping.