Controllable synthesis of α-Bi2O3 and γ-Bi2O3 with high photocatalytic activity by α-Bi2O3→γ-Bi2O3→α-Bi2O3 transformation in a facile precipitation method

Rod-like alpha-Bi2O3 and tetrahedral gamma-Bi2O3 particles have been controlled fabricated by a facile solution crystallization method, which was performed at a mild reaction condition without any surfactants and/or templates. By combining the results of X-ray powder diffraction, high resolution transmission electron microscope, scanning electron microscopy, Xeray photoelectron spectra, and UV-visible absorption spectra, the morphology and crystalline phase evolution of Bi2O3 was studied versus reaction time and reaction temperature. It is interesting to note that the phenomenon of alpha-Bi2O3/gamma-Bi2O3/alpha-Bi2O3 transformation was found. The nanorod alpha-Bi2O3 phase formed in a short time, while alpha-Bi2O3 could transform to tetrahedral gamma-Bi2O3 crystals upon enough reaction time. However, gamma-Bi2O3 may transform into rod-shape alpha-Bi2O3 with further increasing the reaction time. Moreover, it can be deduced that high reaction temperature promoted the transformation from alpha-Bi2O3 to gamma-Bi2O3, and then from gamma-Bi2O3 to alpha-Bi2O3. The photocatalytic activities of Bi2O3 with different crystalline phases were evaluated by the photocatalytic degradation of rhodamine B as a model pollutant. The g-Bi2O3, which exhibits lower electrons-holes recombination rate than that of alpha-Bi2O3, showed excellent photocatalytic activity as compared with the alpha-Bi2O3. (C) 2016 Elsevier B.V. All rights reserved.