Self-assembled hierarchical nanostructures of Bi2WO6 for hydrogen production and dye degradation under solar light

Abstract

Three dimensional (3D) hierarchical nanostructures of orthorhombic Bi₂WO₆ with unique morphologies were successfully synthesized by a solvothermal method. The precursor concentration plays a key role in the architecture of the hierarchical nanostructures. A peony flower-like morphology was obtained at higher precursor concentrations, and a red blood cell (RBC)-like morphology with average diameter of 1.5 μm was obtained at lower concentrations. These hierarchical nanostructures were assembled by self-alignment of 20 nm nanoplates. As their band gap is in the visible region, the photocatalytic activity of the Bi₂WO₆ hierarchical nanostructures for the production of hydrogen from glycerol, and the degradation of rhodamine B (RhB) and methylene blue (MB) under ambient conditions in the presence of solar light was investigated. The Bi₂WO₆ with peony flower morphology was observed to be the most efficient photocatalyst (H₂: 7.40 mmol h⁻¹ g⁻¹, k_RhB: 0.240 and k_MB: 0.100) of the reported nanostructures. The higher activity of the peony flowers was due to their porous nature, high surface area and lower band gap. Such unique 3D nanostructures of Bi₂WO₆ have been fabricated for the first time, and their use as photocatalysts in the production of hydrogen from glycerol has hitherto not been attempted. These nanostructures may have potential in ferroelectric, piezoelectric, pyroelectric and nonlinear dielectric applications.