The composing effect of bismuth on titania hollow microspheres for their visible-light photocatalytic activity

Abstract

Bismuth-composed titania hollow microspheres are fabricated by an impregnation–calcination method using hydrothermally prepared titania hollow microspheres as precursors and Bi(NO₃)₃ as the Bi resource. A series of characterization methods and analyses, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N₂ adsorption–desorption isotherms, Fourier transform infrared spectroscopy and UV-vis spectroscopy were carried out to confirm the successful synthesis of Bi-TiO₂ photocatalysts. The photocatalytic activity is evaluated by photocatalytic decolorization of methyl orange (MO) aqueous solution at ambient temperature under visible-light irradiation. The results show that Bi-composing greatly enhances the visible-light photocatalytic activity of TiO₂ hollow microspheres. When the atomic ratio of Bi/Ti (R_Bi) is increased from 0 to 0.5, the photocatalytic activity of the samples increases. In particular, at R_Bi = 0.5, it shows the highest photocatalytic activity. The Bi-components contain two narrow band gap semiconductors of Bi₂O₃ and Bi₄Ti₃O₁₂ on the surface of TiO₂ hollow microspheres. The results imply that Bi-composing induces the shift of the absorption edge into the visible-light range and the enhancement of visible-light absorption. Furthermore, the formation of the Bi₂O₃/TiO₂ heterojunction and the special multilayer crystal structure of Bi₄Ti₃O₁₂ could efficiently reduce the recombination of photo-generated electrons and holes.