Various bismuth oxyiodide hierarchical architectures: alcohothermal-controlled synthesis, photocatalytic activities, and adsorption capabilities for phosphate in water.

Controllable synthesis of morphology and composition of functional material through a similar method is very necessary to understand the related properties. In this study, we report a facile solvothermal route to synthesize a series of bismuth oxyiodide compounds, including BiOI, Bi7O9I3, and Bi4O5I2 hierarchical microspheres, under relatively mild conditions through only adjusting the types of alcohols. It was found that the viscosity of alcohol played key roles in determining the morphologies and compositions of the final products. UV-visible diffuse-reflectance spectra and theoretic calculations indicated that bismuth oxyiodides with different ratios of Bi:O:I clearly possessed different light absorption and energy band structures. As a result, the as-synthesized BiOI, Bi7O9I3, and Bi4O5I2 hierarchical microspheres displayed morphology- and composition-dependent photocatalytic activities for the degradation of rhodamine B (RhB) and colorless phenol under visible-light irradiation. On the basis of experimental results, the difference of photocatalytic activity of these bismuth oxyiodide compounds was discussed. Furthermore, hierarchical bismuth oxyiodide microspheres were also evaluated as adsorbents for removing phosphate from aqueous solution. The results showed that Bi7O9I3 and Bi4O5I2 hierarchical microspheres had good adsorption capabilities for phosphate in water because of their larger surface areas and hierarchical porous structures.