Correlation Between Morphology Control and Photocatalytic Performance of BiOBr Nano-Microstrutures

Abstract

A systematic approach to optimize the photocatalytic activity of BiOBr nanoparticles was investigated and compared. The resulting BiOBr powders were successfully synthesized through two different pathways: stirred solvothermal and stirred hydrothermal processes under identical synthesis conditions of temperature and time. The composition, morphology, structure and optical properties of as-prepared samples were characterized by means of X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, transmission electron microscopy, diffuse reflectance UV–Visible spectroscopy. Effective surface areas of the synthesized samples were estimated by Brunauer–Emmett–Teller studies. Catalysts prepared by solvothermal process and named (S-BiOBr) were of hierarchical microspheres, while the hydrothermally prepared ones called (H-BiOBr) were nanoflakes, both with a pure crystalline phase. The photocatalytic activities of as-synthesized structures were then examined to evaluate the effect of the synthetic route on the degradation of methyl orange (MO) dye as an organic compound model under simulated solar light irradiation (250 W Xenon lamp, 300 ≤ λ ≤ 800 nm). The photodegradation of MO was monitored by UV–Visible spectroscopy, substantiated by total organic carbon analysis. Hydrothermal process was a non-template method while in solvothermal route ethylene glycol has been used indicating the relative effects of the relationship of medium viscosity on morphology. On the basis of such analysis, the degradation efficiency of S-BiOBr towards MO was found to be 97% compared to 56% using H-BiOBr for 20 ppm concentration of dye. The kinetic analysis confirmed that the reaction rate constant kapp was nearly 3 times higher than that of H-BiOBr, suggesting that S-BiOBr displayed the highest photocatalytic activity for the effective decomposition of MO.