Bi2S3/Bi heterojunction for efficient removal of Cr(VI) via photocatalytic reduction and adsorption

Abstract

It is difficult to remove Cr(VI) from industrial wastewater due to its high toxicity and high mobility. Herein, Bi₂S₃/Bi heterojunction photocatalysts were prepared through vacuum synthesis, in which bismuth oxide (Bi₂O₃) and bismuth sulfide (Bi₂S₃) reacted at high temperatures to generate elemental Bi. To elucidate the mechanism of photocatalytic enhancement, the photocatalytic reduction of Cr(VI) under visible light was analyzed for comparison between Bi₂S₃ and Bi₂S₃/Bi composites. Compared to single Bi₂S₃, Bi₂S₃/Bi performed much better in the reduction rate of Cr(VI) after 30 min of light irradiation, demonstrating its strong adsorption capacity for Cr(III). Moreover, Cr(VI) was still effectively removed after 5 times of reuse. To a large extent, the improvement in photocatalytic performance of Bi₂S₃/Bi is attributed to element Bi forming a new built-in electric field in Bi₂S₃, which facilitates the separation and transport of electrons and holes. In addition, the SPR generated by Bi improves the absorption and reflection of light on the Bi₂S₃ surface, promoting the transfer of electrons. This is a conclusion that can be validated by the photoelectric performance and simulation results. In summary, this study provides crucial reference for the synthesis of photocatalysts and the removal of Cr(VI) from wastewater.