1 College of Materials Science and Engineering, Chongqing Jiaotong University, Chongqing 400074, China 2 School of River and Ocean Engineering, Chongqing Jiaotong University, Chongqing 400074, China
Abstract: In recent years, with the rapid development of industry, the problem of environmental pollution has become increasingly aggravated. Photocatalysis, as an energy-saving and environment-friendly technology with broad application prospects, has become a research hotspot in the field of environmental pollution treatment. In the beginning, the photocatalysts were mainly studied on TiO2, but the activity of TiO2 can only be excited under UV illumination, so numerous visible light excitable photocatalysts were gradually developed at home and abroad. Among them, bismuth bromide oxide (BiOBr) has been regarded as an innovative photocatalyst due to its unique optical properties and special electronic structure. However, the short wavelength range of visible light absorption of pure BiOBr is the bottleneck of its practical application. Nowadays, coupling with other semiconductors possessing excellent visible light absorption capacity has been considered an effective method to improve the photocatalytic performance of BiOBr phototalysts. In this study, an efficient binary three-dimensional spherical Bi2S3/BiOBr hierarchical heterostructure photocatalyst composed of lamellar BiOBr and rod-like Bi2S3 was constructed via a one-step solvothermal route. The obtained samples with different Bi2S3 contents were characterized by X-ray powder diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The structural analysis showed that the nano-flower-like Bi2S3/BiOBr three-dimensional spheres were successfully prepared and a tight interfacial connection was formed between the two components. The photocatalytic tests revealed that the catalytic properties of the composites were highly dependent on the Bi2S3 content. Moreover, the 12.5%-Bi2S3/BiOBr composite exhibited the maximum activity for RhB degradation under visible light illumination, which was 4.2 times and 39.6 times higher than that of the BiOBr and Bi2S3 components, respectively. The mechanism of enhanced photocatalytic activity was proposed based on photoluminescence analysis, photocurrent measurements, electrochemical impedance and UV diffuse reflectance spectroscopy. The enhanced photocatalytic performance of the Bi2S3/BiOBr composites was mainly attributed to the formation of an effective heterojunction structure between the components, which led to an increase in carrier separation efficiency and an expansion of the visible light absorption range. The trapping experiments of active species showed that the degradation of RhB was mainly from the oxidation of cavities, followed by the action of superoxide radicals. The formation of superoxide radicals was found to be related to dye sensitization by energy band calculations and experimental analysis. The reusability test study showed that the 12.5%-Bi2S3/BiOBr samples still showed good stability and reusability after multiple cycles of degradation. Therefore, RhB removal by Bi2S3/BiOBr indicates the potential of the as-prepared composite to degrade other types of organic compounds for wastewater purification and environmental remediation applications.
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