Bi₂O₃ hierarchical nanostructures: Controllable synthesis, growth mechanism, and their application in photocatalysis

By introducing VO₃^- into the reaction system, uniform hierarchical nanostructures of Bi₂O₃ have been successfully synthesized by a template-free aqueous method at 60-80°C for 6 h. The as-prepared hierarchitectures are composed of 2D nanosheets, which intercross with each other. Based on the electron microscope observations, the growth of such hierarchitectures has been proposed as an Ostwald ripening process followed by self-assembly. The nucleation, growth, and self-assembly of Bi₂O₃ nanosheets could be readily tuned, which brought different morphologies and microstructures to the final products. Pore-size distribution analysis revealed that both mesopores and macropores existed in the product. UV-vis spectroscopy was employed to estimate the band gap energies of the hierarchical nanostructures. The photocatalytic activities of as-prepared Bi₂O₃ hierarchitectures were 6-10 times higher than that of the commercial sample, which was evaluated by the degradation of RhB dye under visible light irradiation (λ > 420 nm).