Elucidating the structure-dependent photocatalytic properties of Bi2WO6: a synthesis guided investigation

Abstract

Polycrystalline microspheres and single-crystalline microplates of Bi₂WO₆ have been synthesized by ultrasonic spray pyrolysis. Herein, these materials are evaluated as photocatalysts for the visible light mediated degradation of rhodamine B, a model pollutant, and the results compared to those obtained with Bi₂WO₆ prepared by traditional methods. The microplates, which displayed the best crystallinity and highest surface area, were anticipated to facilitate the greatest rate of dye photodegradation. However, the polycrystalline microspheres outperformed both the Bi₂WO₆ microplates and traditional samples. To understand the origin of this result, the local and macroscale structures of the Bi₂WO₆ samples were comprehensively characterized by spectroscopy techniques (diffuse reflectance, fluorescence, Raman, and X-ray photoelectron spectroscopy) as well as electron microscopy and diffraction. This analysis found that the enhanced performance of the Bi₂WO₆ microspheres results from the expression of a hydrophilic surface, a low concentration of point defects, and a moderate surface area. This finding highlights the significant role synthesis plays in imparting structure and functionality to solid materials.