Construction of fast charge-transferred 0D/2D BiOBr/Bi2WO6 S-scheme heterojunction with enhanced photocatalytic performance

Novel Bi-based photocatalysts play an increasing role in dealing with environmental pollution and resource shortages. Among these Bi-based materials, BiOBr and Bi2WO6 have gained intensive attraction due to the appropriate energy band alignments and their anisotropic crystal structure. 0D/2D BiOBr/Bi2WO6 heterojunction was constructed by depositing BiOBr nanoparticles on few-layer Bi2WO6 nanosheets. The structure, optical property, and micromorphology of samples were characterized by XRD, XPS, UV–vis DRS, SEM, TEM, and AFM. The photoluminescence, photocurrent density, and electrochemical impedance spectroscopy (EIS) as well as the transient surface photovoltage (TSPV) were performed to explore the transfer of photoinduced charge carriers. The photocatalytic efficiency of the heterojunction is much improved, about 2.67 folds higher than that of pristine Bi2WO6. The fast separation and migration and the prolonged lifetime of photogenerated carriers in the BiOBr/Bi2WO6 heterojunction are validated by photoelectrochemical tests. The influence factors, versatility, and reusability of the heterojunction are also evaluated. Radical trapping test reveals that h+ and ·O2− are predominant active species and make a major contribution to the photoactivity of the BiOBr/Bi2WO6 heterojunction. The formed energy-band bending, the built-in electric field, and the S-scheme charge transfer strategy are thermodynamically and kinetically favorable for the photoactivity and stability of the heterojunction.