Surfactant-free hydrothermal synthesis of hierarchical flower-like Bi2WO6 mesosphere nanostructures with excellent visible-light photocatalytic activity

Hierarchical flower-like Bi2WO6 mesosphere nanostructures self-assembled with nanosheets were synthesized by hydrothermal treatment of an aqueous suspension of Bi(NO3)3·5H2O and Na2WO4·2H2O without surfactants or mineralizers. The as-prepared hierarchical flower-like Bi2WO6 mesosphere nanostructures were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, selected-area electron diffraction, and nitrogen adsorption–desorption isotherms. To understand the formation mechanism of the hierarchical flower-like Bi2WO6 mesosphere nanostructures, a series of time-dependent experiments were carried out. In general, the synergistic effects of the higher solubility of bismuth subnitrate on the nucleation and adsorption of subnitrate radicals on the surfaces of (010) planes and combination with Bi3+ situated at (010) planes resulted in primary Bi2WO6 nanosheets of very smaller thickness and lateral size. To minimize further the system energy, the formed Bi2WO6 nanosheets self-assembled to hierarchical flower-like Bi2WO6 mesosphere nanostructures. In addition, the band gap and photocatalytic activity of the hierarchical flower-like flower-like Bi2WO6 mesosphere nanostructures were investigated by UV-vis absorption and we used it as a photocatalyst to degrade rhodamine B.