Self-Assembled Three-Dimensional Hierarchical Umbilicate Bi₂WO₆ Microspheres from Nanoplates: Controlled Synthesis, Photocatalytic Activities, and Wettability

Self-assembled three-dimensional (3D) hierarchical umbilicate Bi 2 WO 6 microspheres from nanoplates have been synthesized by a new controllable hydrothermal route on a large scale. It was found that citrate played multifold roles in the formation process of Bi 2 WO 6 hierarchical microspheres in our reaction system. In order to obtain well-assembled Bi 2 WO 6 microspheres, NaHCO 3 was used to adjust pH values of the reaction solution and establish a buffer system by the equilibrium of the formation and dissociation of carbonic acid. On the basis of XRD analysis and TEM observation of the products at the different reaction time periods, the formation mechanism of Bi 2 WO 6 hierarchical microspheres was proposed. UV−vis diffuse reflectance spectra indicated that as-synthesized Bi 2 WO 6 hierarchical microspheres had absorption in both UV and visible light areas. The BET surface area of the sample was ca. 24.1 m 2 /g, which was 35 times higher than that of the Bi 2 WO 6 powder prepared by the solid-state reaction method. The hierarchical umbilicate Bi 2 WO 6 microspheres exhibited good photocatalytic activity in degradation of Rhodamine-B (RhB) under 150 W Xe lamp light irradiation. In addition, the wettability of Bi 2 WO 6 films fabricated by as-obtained Bi 2 WO 6 microspheres was also studied.