Preparation and effects of calcining temperature and pH on the photocatalytic activity of BiVO4 microcrystal for degrading methylene blue

BiVO4 photocatalysts were synthesized by a polyacrylamide gel method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirmed the formation of monoclinic BiVO4. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations showed that BiVO4 had the morphology of sphere-like particles and smooth surface. Ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) data demonstrated that the band gaps of BiVO4 particles varied in the range of 2.34 to 2.49 eV. Photoluminescence (PL) spectra revealed that BiVO4 obtained at a lower calcining temperature had the weaker emission intensity and the lower recombination rate of photogenerated carriers. The influences of different calcination temperatures and pH values on the photocatalytic activities were evaluated by degrading methylene blue (MB) solution under visible light irradiation. BiVO4 prepared by calcining xerogel at 500 ℃ possessed the highest photocatalytic activity as high as 96.542% after 180 min. The photocatalytic efficiency of BiVO4 particles under alkaline conditions was higher than that under acidic conditions. Trapping experiments verified that singlet oxygen (1O2), superoxide radical (·O2−), and hydroxyl radical (·OH) were the principal active species in the photocatalytic reactions. The as-obtained BiVO4 photocatalysts exhibit great potential in pollutant removal.