A new perspective for effect of Bi on the photocatalytic activity of Bi-doped TiO2

In the current work, a simple approach, directly mixing Bi2O3 powder with TiO2 sol, was developed to fabricate Bi-doped TiO2 photocatalyst. The obtained product was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM). Raman spectra analysis, X-ray photoelectron spectra (XPS) and UV-vis diffuse reflectance spectroscopy (DRS). On the basis of the above characterization results, it was found that the excess Bi2O3 loading (>5 mol%) and sol-gel processing route could lead to the formation of BixTiOy. The XRD data pointed out that BixTiOy remained amorphous up to 500 degrees C and crystallized into the distinctive phase Bi2Ti4O11 at higher temperature of 700 degrees C. It was worth mentioning that the participation of the distinctive microstructures made the finishing point of the doped photocatalyst, that is, strong spectral response in visible region and marked activity during the photooxidation of gaseous benzene under visible light illumination (lambda > 450 nm). Furthermore, the calcination temperature also had an important effect on the photocatalytic activity. The optimal dosage of 10 mol% Bi in TiO2 and sintering temperature of 400 degrees C achieved the best photocatalytic activity. Finally, the amorphous BixTiOy microstructures formed in TiO2 crystal made a significant contribution in providing large specific surface area and more activated units regarding the photocatalytic process. It is hoped that our current work will contribute to a better understanding of the existence form of bismuth in TiO2 crystal. More generally. it suggests the incorporation of bismuth into a simple oxide of wide band gap as a strategy to design photocatalysts with excellent properties. (C) 2012 Elsevier B.V. All rights reserved.