Construction of a hydrangea-like Bi2WO6/BiOCl composite as a high-performance photocatalyst

Abstract

The microstructure design and construction of a heterojunction are major strategies for enhancing the photocatalytic activity of semiconductors. Herein, Bi₂WO₆ flower spheres were synthesized and acted as a porous template for depositing BiOCl to fabricate a Bi₂WO₆/BiOCl composite photocatalyst. Through changing the concentrations of the Bi³⁺ and Cl⁻ precursors, a hydrangea-like Bi₂WO₆/BiOCl composite with a porous nanostructure was synthesized. Rhodamine B (RhB), methylene blue (MB) and tetracycline hydrochloride (TCH) were selected as simulated pollutants for degradation by the photocatalyst. Under the irradiation of visible light, the optimized Bi₂WO₆/BiOCl composite removes almost 100% of RhB from solution in 60 min, 88% of MB in 75 min, and 90% of TCH in 90 min, much better than the performances of pure Bi₂WO₆ or BiOCl. The excellent photocatalytic activity of the Bi₂WO₆/BiOCl composite can be attributed to its hydrangea-like nanostructure and Bi₂WO₆/BiOCl heterojunction. On the one hand, the hydrangea-like structure promotes the physical adsorption of organic molecules on the photocatalyst. On the other hand, the Bi₂WO₆/BiOCl heterojunction broadens the light absorption range, accelerates the separation of photogenerated electrons and holes, and decreases charge transfer resistance, further improving the photocatalytic activity of the material. ˙O₂⁻ and ˙OH reactive species were generated under visible light irradiation, which promoted the fast degradation of organic pollutants. Based on the reactive species and the position of its conduction/valence band, the photocatalytic mechanism of the Bi₂WO₆/BiOCl composite was proposed as a Z-scheme heterojunction transfer mode.