Bi4O5I2 flower/Bi2S3 nanorod heterojunctions for significantly enhanced photocatalytic performance

Abstract

Optimally engineered heterojunctions are of great interest to pursue higher photocatalytic activity in a wide range of applications. A series of controlled Bi₄O₅I₂/Bi₂S₃ heterojunctions have been fabricated through a solvothermal method combined with an anion exchange process. The in situ growth of Bi₂S₃ nanorods from Bi₄O₅I₂ flowers reveals that there exist strong coupling and intimate interfaces between the two semiconductors. The Bi₄O₅I₂/Bi₂S₃ heterojunctions exhibit excellent photocatalytic activities and stability in the photocatalytic reduction of Cr(VI) under visible light irradiation (λ > 420 nm). The highest apparent rate constant is up to 0.05614 min⁻¹, which is about 56 and 7.5 times that of pristine Bi₄O₅I₂ and Bi₂S₃, respectively. Further detailed characterization reveals that the drastically enhanced and stable Cr(VI) reduction can be attributed to the efficient transfer and spatial separation of the photo-induced carriers, resulting in strong light harvesting. It results from not only the synergetic effects of Bi₂S₃ sensitization and heterojunctions with matched band structures, but also the unique flower/nanorod architecture and intimate contact at the molecular scale between Bi₄O₅I₂ and Bi₂S₃. It also provides critical insights into the underlying pathways involved in the photocatalytic reduction of Cr(VI) over Bi-based heterojunctions.