Controllable Preparation Of Bismuth-based Composite Semiconductors In Solution Phase And Photocatalytic Properties Study

This paper was committed to study preparation, characterization and photocatalytic properties of bismuth-based composite materials. The main research work is listed as the following parts:(1) Hollow olive-shaped BiVO₄ microspheres was successfully synthesized in the presence of AOT under mixed solvothermal conditions at 160 oC for 18 h on a large scale. Furthermore, core-shell BiVO₄@Bi₂O₃ was obtained by thermal solution etching route, employing olive-shaped BiVO₄ as precursors. The as-obtained products were characterized by X-ray diffraction (XRD), Field-emission scanning electron microscope (FE-SEM), Transmission electron microscope (TEM), BET specific surface area, and UV-vis diffuse reflectance spectroscopy in detail. The influences of surfactant and the ratios of mixed solvents on the resultant products were systematically surveyed. The formation process of hollow olive-shaped BiVO₄ was investigated through the X-ray diffraction analyses and scanning electron microscope observations of the intermediate products at the different reaction stages. The photocatalytic properties of the as-obtained hollow olive-shaped BiVO₄ and core-shell BiVO₄@Bi₂O₃ were compared. The results indicated that core-shell BiVO₄@Bi₂O₃ exhibited much higher photocatalytic activities than pure olive-shaped BiVO₄. The mechanism of enhanced photocatalytic activity of core-shell BiVO₄@Bi₂O₃ was proposed on the basis of theoretical calculation.(2) Bi₂S₃/BiVO₄ composite photocatalysts were successfully synthesized through a chemical conversion route under hydrothermal conditions, employing olive-shaped BiVO₄ as precursors and Thioacetamide (TTA) as sulfur resource. The as-obtained products were characterized by X-ray diffraction (XRD), Field-emission scanning electron microscope (SEM), UV-vis diffuse reflectance spectroscopy, Photoluminescence spectra and EDX spectra in detail. The photocatalytic properties of the as-obtained BiVO₄ and Bi₂S₃/BiVO₄ composite photocatalysts were compared. The results indicated that Bi₂S₃/BiVO₄ composite photocatalysts exhibited much higher photocatalytic activities than pure BiVO₄. It was found that Bi₂S₃/BiVO₄ composite semiconductor prepared with molar ratio of BiVO₄: TAA=1:0.4 shows the best photocatalytic acticity. Combined with theoretical calculation of band-edge positions of the two semiconductors, the mechanism of enhanced photocatalytic activity of Bi₂S₃/BiVO₄ was proposed.(3) Bi₂WO₆/CNTs composite photocatalysts were synthesized under hydrothermal conditions, using carboxylated carbon nanotubes as supports. The as-obtained products were characterized by X-ray diffraction (XRD) and Field-emission scanning electron microscope (FE-SEM) in detail. The influence of the concentration of reactants on the morphology of resultant products was studied by field-emission scanning electron microscope. The photocatalytic results shows Bi₂WO₆/CNTs nanocomposite materials have good photocatalytic performance on the degradation of Rhodamine B under visible-light irradiation (λ>400nm).