Fabrication of flower-like Bi2WO6 superstructures as high performance visible-light driven photocatalysts

A novel flower-like Bi2WO6 superstructure was successfully realized by a facile hydrothermal process without any surfactant or template. Based on the evolution of this morphology as a function of hydrothermal time, the formation mechanism was proposed to be as follows: (1) self-aggregation of nanoparticles; (2) formation of crystalline nanoplates by Ostwald ripening; and (3) organization of the in situ-formed nanoplates into spherical superstructures. The pretty flower-like superstructure of Bi2WO6 was retained after calcination at 550 °C for 4 h. Both the uncalcined and calcined Bi2WO6 exhibited excellent visible-light-driven photocatalytic efficiencies for the degradation of Rhodamine B (RhB), up to 84 and 97% within 60 minutes, respectively, which were much higher than those of TiO2 (P-25) and Bi2WO6 sample prepared by solid-state reaction (SSR-Bi2WO6). Close investigation indicated that plenty of pores with different sizes existed in the Bi2WO6 superstructures, which could serve as hierarchical transport paths for small molecules and might greatly improve their photocatalytic activities.