We report a facile template-free solvothermal approach for the synthesis of Bi2WO6 hierarchical structures assembled by porous nanoplates, the unique morphology of which endows the sample with high photocatalytic activity under visible light irradiation. The synthesized Bi2WO6 hierarchical structures have diameters of ~1 μm, and consist of multiple crossed-plates in three-dimensional configuration. A possible three-stage formation mechanism was proposed for the construction of hierarchical structures, and Ostwald ripening was responsible for the formation of meso-pores. The as-prepared Bi2WO6 hierarchical structures exhibited high photocatalytic activity on the degradation of Rhodamine B under visible light irradiation, due to the larger specific surface area (20.4 m2 g−1), unique hierarchical structures with multiple-crossed porous layer and higher crystallinity. A comparison of photocatalytic performance between the hierarchical structures and other samples with different morphologies was performed. The main active species of Bi2WO6 hierarchical structures during a photocatalytic process were determined to be O2− and h+ radicals by dissolving different trapping agents.

Photocatalytic activity evaluation

The photocatalytic properties of the products  for the degradation of RhB were evaluated undervisible light irradiation. Photocatalytic experiments were conducted as follows . 100mg of as-prepared samples was dispersed in Rhb solution (1.0*10-5 M, 10ml) and then magnetically stirred in dard for 60 min to reach adsorption equilibrium and uniform dispersibility. The solution was exposed to visible light irradiation from a 300W Xenon lamp with 420 nm cut-off filter(CEL-HXF 300, Beijing Aulight, China, I=15A) at room temperature. During the irradiation, the suspension was magnetically stirred using a magnetic stirrer.  At given time intervals(10min)