Facile synthesis and photocatalytic activity of hierarchical WO3 core–shell microspheres

In this work, we present a facile template-free precipitation method for the large-scale preparation of hierarchical WO3 core–shell microspheres in which the core was composed of aggregated nanoparticles encapsulated by a hierarchical shell layer self-assembled by ultrafine nanoplates with a thickness of about 15 nm. The products are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), differential scanning calorimetry and thermogravimetry (TG/DSC). The experimental parameters affecting the morphology were discussed in detail. We found that the concentration of citric acid and pH value of the reaction solution had profound effects on the morphology of the products. In addition, a formation mechanism was proposed for producing hierarchical WO3 core–shell microspheres. Furthermore, the obtained hierarchical WO3 core–shell microspheres showed superior photocatalytic activities for the degradation of rhodamine B (RhB) under visible light irradiation.