Hierarchical Bi2WO6/TiO2-nanotube composites derived from natural cellulose for visible-light photocatalytic treatment of pollutants

A series of Bi2WO6/TiO2-nanotube (Bi2WO6/TiO2-NT) heterostructured composites were prepared by utilizing natural cellulose (e.g., laboratory filter paper) as the structural template. The obtained nanoarchitectonics, namely Bi2WO6/TiO2-NT nanocomposites, displayed three-dimensionally interwoven structures which replicated the initial cellulose template. The composite Bi2WO6/TiO2-NT nanotubes were formed by TiO2 nanotubes that uniformly anchored with Bi2WO6 nanoparticles of various densities on the surface. The composites exhibited improved photocatalytic activities toward the reduction of Cr(VI) and degradation of rhodamine B under visible light (lambda > 420 nm), which were attributed to the uniform anchoring of Bi2WO6/TiO2 nanoparticles on TiO2 nanotubes, as well as strong mutual effects and well-proportioned formation of heterostructures in between the Bi2WO6/TiO2 and TiO2 phases. These improvements arose from the cellulose-derived unique structures, leading to an enhanced absorption of visible light together with an accelerated separation and transfer of the photogenerated electron-hole pairs of the nanocomposites, which resulted in increased effective amounts of photogenerated carriers for the photocatalytic reactions. It was demonstrated that the photoinduced electrons dominated the photocatalytic reduction of Cr(VI), while hydroxyl radicals and reactive holes contributed to the photocatalytic degradation of rhodamine B.