Synthesis of homogeneous sphere-like Bi2WO6 nanostructure by silica protected calcination with high visible-light-driven photocatalytic activity under direct sunlight

The homogeneous sphere-like morphology of bismuth tungstate (Bi2WO6) was synthesized by silica protected calcination using a facile hydrothermal method followed by silica etching. The flower-like Bi2WO6 structure was synthesized without silica protection. SEM and TEM analysis of the samples at different hydrothermal reaction times reveals that the growth of in situ formed nanoplates was controlled by silica protection which leads to the formation of the sphere-like structures of Bi2WO6. The homogeneous sphere-like structure was retained up to 1 h of etching period with complete removal of the silica layer. Subsequently, both the flower and sphere-like Bi2WO6 were used as photocatalysts for the degradation of reactive black 5 (RB5) dye under direct sunlight irradiation. Sphere-like Bi2WO6 exhibited excellent visible-light-driven photocatalytic efficiencies by complete degradation of the RB5 dye within 3 h compared with the flower-like Bi2WO6 (45%, 3 h) structure. The enhancement in photocatalytic activity using homogeneous sphere-like Bi2WO6 was confirmed by kinetic studies, chemical oxygen demand, total organic carbon and total inorganic carbon analysis.