One-Pot Template-Free Hydrothermal Synthesis of Monoclinic BiVO_(4) Hollow Microspheres and Their Enhanced Visible-Light Photocatalytic Activity

摘要

Monoclinic-phase BiVO_(4) hollow microspheres with diameters of about 2-4 (mu)m have been successfully fabricated in high yield by a one-pot template-free hydrothermal route. The reaction duration and urea concentration are shown to play important roles in the formation of the BiVO_(4) hollow microspheres. X-ray diffraction, scanning electron microscopy, nitrogen adsorption-desorption isotherms, fourier transform infrared spectrometry, and UV-visible diffuse reflectance spectroscopy are used to characterize the products. The results show that all the as-prepared BiVO_(4) samples have monoclinic phase structure and exhibit good crystallinity. A formation mechanism for the BiVO_(4) hollow spherical structure via a localized Ostwald ripening is proposed based on the experimental observations. In addition, studies of the photocatalytic properties by exposure to visible light irradiation demonstrate that the as-obtained BiVO_(4) hollow spheres show potential photocatalytic application. Hydroxyl radicals ((centre dot)OH) are not detected on the surface of visible-light-illuminated BiVO_(4) by the photoluminescence technique, suggesting that (centre dot)OH is not the dominant photooxidant and photogenerated hole could directly take part in photocatalytic reaction. The prepared BiVO_(4) hollow spheres are also of great interest in pigment, catalysis, separation technology, biomedical engineering, and nanotechnology.