Low-temperature synthesis of δ-Bi 2 O 3 hierarchical nanostructures composed of ultrathin nanosheets for efficient photocatalysis

Due to its highest conductivity of any oxide material, the delta phase of Bi2O3 (δ-Bi2O3) is recognized as one of the most technologically important materials for various applications, including photocatalysis. Nevertheless, the δ-Bi2O3 phase is not stable at room temperature. Herein, we demonstrate that δ-Bi2O3 can be synthesized at low temperature through a facile sol-gel route in the presence of metavanadate oxyanion (VO3−). The chemical state and local structure of V are investigated by synchrotron-based techniques, such as X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Our findings demonstrate the critical role of VO3− in stabilizing the δ-Bi2O3 phase. The crystallinity of δ-Bi2O3 is dramatically increased by the addition of VO3−. In the absence of VO3−, amorphous product is obtained. The as-synthesized δ-Bi2O3 possesses 3D hierarchical nanostructures constructed by ultrathin nanosheets with a few nanometers thick (~ 5 nm). The nanosheets are composed of ultrasmall nanoparticles in the range of 1–2 nm in size. Such a unique hierarchitecture of δ-Bi2O3 allows efficient light utilization due to multiple reflections and scattering, indicated by its excellent photocatalytic activity for the degradation and mineralization of atrazine in aqueous solution.