Template and surfactant free synthesis of hierarchical WO ₃·0.33H₂O via a facile solvothermal route for photocatalytic RhB degradation

A template- and surfactant-free solvothermal method has been successfully developed for the controlled synthesis of 3D micro-dahlia WO₃· 0.33H₂O hierarchical structures with single-crystalline petals for the first time. In this reaction system, acetone plays a key role due to the high saturated vapour pressure, high solubility of the precursor, low solvent polarity, and its organic groups. The optimum volume ratio of water and acetone is 2 to 1 for the formation of perfect micro-dahlia hierarchical structures. Based on scanning electron microscopy and transmission electron microscopy observations and experimental results, the reaction process and growth mechanism of such a hierarchitecture were proposed. Moreover, UV-vis absorption measurements demonstrated that visible light absorption of the products increased gradually with the increasing volume of acetone. The photocatalytic activity of micro-dahlia WO₃·0.33H₂O was higher than that for the sample synthesized using water as the solvent. After 240 minutes of the photodegradation process, 88.5% of RhB was eliminated by the hierarchical micro-dahlia WO₃·0.33H₂O.