Preparation of BiVO₄ Hollow Spheres and its Photocatalytic Degradation of Methylene Blue

Monoclinic BiVO₄ hollow nanospheres were successfully prepared via template-free method using citric acid (C₆H₈O₇) as chelating agent and characterized by X-ray diffraction patterns, transmission electron microscope, UV-Vis DRS, and TG-DTA technique. C₆H₈O₇ played an important role in the formation of hollow spheres. Morphology observations revealed that when appropriate amount ofC₆H₈O₇ was introduced, the cavity with the diameter of 40 nm was obtained in BiVO₄ nanospheres. UV-Vis diffuse reflectance spectra indicated that the samples had absorption in both UV and visible light region. The photocatalytic activities were evaluated by the degradation of methylene blue under Xe lamp irradiation. Hollow spheres endow BiVO₄samples with greatly improved photocatalytic activity. A possible formation mechanism of hollow spheres was proposed.