Titanium alkoxide induced BiOBr–Bi2WO6 mesoporous nanosheet composites with much enhanced photocatalytic activity

Abstract

Here we report a facile hydrothermal route for the preparation of BiOBr–Bi₂WO₆ mesoporous nanosheet composites (MNCs) in the presence of titanium isopropoxide, Ti(OⁱPr)₄. High resolution transmission electron microscopy, X-ray diffraction, nitrogen adsorption/desorption analysis and X-ray photoelectron spectroscopy were employed for structural and composition analyses of the MNCs. The photogenerated charge transfer and photocatalytic activity of BiOBr–Bi₂WO₆ MNCs were investigated by Kelvin probe force microscopy and UV-vis spectroscopy. We propose mechanisms to illustrate how titanium alkoxide induces the formation of mesoporous nanosheet heterostructures and the enhanced photodecomposition efficiency of the dye under low light intensity illumination. Overall, our results suggest that titanium alkoxide is not only strongly involved in the growth of BiOBr (001) facets, but also plays a critical role in the pore evolution of the product. Kelvin probe force microscopy analysis allows us to conclude that the resulting nanocomposites demonstrate high photogenerated charge mobility and a long lifetime. Dye molecules can be rapidly and thoroughly decomposed with the photocatalyst under very low light intensity illumination. The enhanced photocatalytic activity is attributed to well matched band edge positions of BiOBr and Bi₂WO₆ and the large specific surface area of the MNCs in view of the incorporation of mesopores and the highly exposed BiOBr (001) facet due to the use of Ti(OⁱPr)₄ during the synthesis. The results presented here are expected to make a contribution toward the development of delicate nanocomposites for photocatalytic water purification and solar energy utilization.