Photocatalytic Activity of Sol-Gel Derived Bi₂O₃-TiO₂ Nanocomposite

Abstract

Bi 2 O 3 -TiO 2 nanocomposites were obtained by sol-gel method using tween 80 (T-80) or polyvinyl pyrrolidone-polyethylene glycol (PVP-PEG) as templating agent. The powder X-ray diffraction (XRD) patterns of both the composites reveal the crystal structure of Bi 2 O 3 as primitive tetragonal and TiO 2 is in anatase phase. The energy dispersive X-ray (EDX) spectra provide the composition of Bi 2 O 3 in Bi 2 O 3 -TiO 2 (T-80) and Bi 2 O 3 -TiO 2 (PVP-PEG) as 3.8 and 20.4 mol. %, respectively. The average crystallite sizes of Bi 2 O 3 -TiO 2 (T-80) and Bi 2 O 3 -TiO 2 (PVP-PEG), derived from XRD, are 9 and 17 nm, respectively. The scanning electron microscopic (SEM) images show the spherical shape of Bi 2 O 3 -TiO 2 (T-80) and the composites are polycrystalline. The diffuse reflectance spectra (DRS) of the composites display faint absorption of visible light and strong absorption in UV-A region. The photoluminescence (PL) spectra of both the composites are similar and the observed near band gap emission (NBE) and deep level emission (DLE) agree with those of TiO 2 . The impedance spectra show that the charge-transfer resistances of the composites do not differ significantly. The visible light photoimpedance spectra display the photoconductance of Bi 2 O 3 -TiO 2 (PVP-PEG) but not that of Bi 2 O 3 -TiO 2 (T-80). Although the visible light-photocatalytic activities of the two nanocomposites to degrade dye do not differ significantly Bi 2 O 3 -TiO 2 (T-80) under UV-A light degrades dyes faster than Bi 2 O 3 -TiO 2 (PVP-PEG).