Synergistic effect of crystal and electronic structures on the visible-light-driven photocatalytic performances of Bi2O3 polymorphs

Abstract

Three polymorphs of Bi₂O₃ were selectively synthesized via solution-based methods. The phase structures of the as-prepared samples were confirmed by X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). UV-vis diffuse reflectance spectroscopy was employed to study the optical properties of Bi₂O₃ polymorphs, and the band gaps were estimated to be 2.80, 2.48, and 3.01 eV for α-Bi₂O₃, β-Bi₂O₃, and δ-Bi₂O₃, respectively. The photocatalytic performances of the oxides were investigated by decomposing methyl orange and 4-chlorophenol under visible irradiation at room temperature. It was observed that β-Bi₂O₃ displayed much higher photocatalytic performance than N-doped P25. Among the three polymorphs of Bi₂O₃, the photocatalytic activities followed the order: β-Bi₂O₃ > α-Bi₂O₃ > δ-Bi₂O₃, which was in good accordance with the photoluminescence spectra measurement results. The synergistic effect of the crystal and electronic structures on the photocatalytic performances of Bi₂O₃ polymorphs was investigated. The much better photocatalytic activity of β-Bi₂O₃ was considered to be closely related to its smaller band gap, higher crystallinity and unique tunnel structure.