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

Abstract

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.