Oxygen vacancies enriched Z-scheme BiOI/Bi2O3 heterojunction with controllable band-gap for dye degradation and Cr (VI) reduction

Abstract

This study successfully synthesized the wrinkled Z-scheme BiOI/Bi₂O₃ heterojunction with controllable band-gap energy by a co-precipitation method. The wrinkled structure regulated by CH₃COOH as a structural modifier would enhance the utilization of visible light, and the oxygen defects generate a large number of active sites within BiOI/Bi₂O₃ heterojunctions. With an increase in the concentration of HAc, the band-gap energy (E_g) of the BiOI/Bi₂O₃ could be modulated from 1.75 to 1.96 eV. To assess the photocatalytic efficiency, the synthesized BiOI/Bi₂O₃ was further employed for Cr(VI) reduction as well as degradation of Methyl Blue (MB) and Rhodamine B (RhB). The heterojunction of BiOI/Bi₂O₃-2, possessing an energy gap (E_g) of 1.86 eV, demonstrated the optimized photocatalytic efficiency of 97.2 %, 97.3 %, and 98.6 % for Cr(VI) reduction, MB and RhB degradation, respectively. In addition, the Z-scheme BiOI/Bi₂O₃ heterojunction has high reduction efficiency in the Cr (VI) of natural wastewater. Radical capture experiments and ESR spectroscopy emphasized the primary importance of species in the Cr(VI) reduction, while highlighting the primary role of e⁻, ·O₂⁻ and h⁺ species in the MB and RhB degradation. The work provided a straightforward and efficient strategy for modulating the energy gap (E_g) of the wrinkled BiOI/Bi₂O₃ heterojunction, while also exploring the intricate correlation between E_g and photocatalytic activity. The photocatalytic enhancement effect demonstrated by the BiOI/Bi₂O₃ could be applied in various domains of photocatalysis, thereby offering valuable insights for designing multifunctional and highly active photocatalysts.