Visible-light photocatalytic degradation of RhB by Bi₂O ₃ polymorphs

The α, βand γ-Bi₂O₃ were obtained by a chemical precipitation method. The crystal structures, morphologies and optical properties of Bi₂O₃ polymorphs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption method, thermal gravimetry-differential scanning calorimetry (TG- DSC) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The photocatalytic performance of Bi₂O was evaluated using 3rhodamine B (RhB) as a model pollutant under visible light illumination (λ>420 nm). The result showed that the lath-shaped α-Bi₂O₃ with a band gap of 2.84 eV was 3 |μm in length and 1 |xm in width; the irregular β-Bi₂O₃ with a band gap of 2.75 eV had a particle size of approximately 150 nm; the nanotube γ-Bi₂O ₃ with a band gap of 2.68 eV was 6 nm in diameter and 150 nm to 200 nm in length. The photocatalytic degradation of RhB by Bi203 polymorphs under visible light illumination were as follows: γ-Bi₂O ₃>β-Bi₂O₃<α-Bi ₂O₃ The y-Bi₂O₂ nanotube exhibited the est photocatalytic performance which can effectively degrade 91% RhB within 60 min.