Hierarchical Bi7O9I3 micro/nano-architecture: facile synthesis, growth mechanism, and high visible light photocatalytic performance

Bi7O9I3, a fresh member of the bismuth oxyhalide family, with hierarchical micro/nano-architecture is successfully synthesized by a one-step, template and surfactant-free solution method. The as-prepared product was characterized by various techniques. X-ray diffraction, X-ray photoelectron spectroscopy and thermogravimetric analysis confirm that the composition of the as-fabricated sample is Bi7O9I3. Scanning and transmission electron microscopy observations reveal that the as-synthesized sample exhibits a microsized plate-like structure with dense nanosheets standing on their surfaces. The time-dependent morphology of the Bi7O9I3 sample was investigated, and a possible formation mechanism of the hierarchical structure is proposed. More importantly, the Bi7O9I3 exhibits an excellent photocatalytic activity in the degradation of phenol under visible light irradiation. The high catalytic performance of the Bi7O9I3 hierarchical structure comes from its electronic band structure, high surface area and high surface-to-volume ratio. In addition, the Bi7O9I3 hierarchical architecture is stable during the reaction and can be used repeatedly. The present work not only gives insight into understanding the hierarchical growth behaviour of complex bismuth oxide iodide structures in a solution-phase synthetic system, but also provides a new way to improve the photocatalytic performance by designing desirable structures and morphologies.