| BiVO4 has been recognized as a visible-light-responsive semiconductor photocatalyst. It usually exists in three kinds of crystalline structures: tetragonal zircon, monoclinic scheelite, and tetragonal scheelite. Among the three crystalline forms, the monoclinic scheelite shows the best photocatalytic performance under visible-light illumination. In the thesis, monoclinic BiVO4 single-crystallites with regular morphologies or porous structures were fabricated using different methods. The physicochemical properties of these materials were characterized by means of the techniques, such as Xay-ray dfiffraction (XRD), thermogavimetric analysis (TGA), differential scanning calorimetry (DSC), Laser Raman spectroscopy, high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), N2 adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible duffuse reflectance spectroscopy (UV-Vis). The photocatalytic performance of the as-fabricated BiVO4 samples was measured for the photodegradation of methylene blue (MB) under visible-light irradiation. The results are as follows:1. With bismuth nitrate and sodium vanadate as metal sourse and aqueous ammonia solution as pH adjustor, monoclinic BiVO4 single-crystallites with polyhedral, hyperbranched, polyhedral, and spherical morphologies were fabricated using the surfactant-free hydrothermal route at pH = 1, 3, 6, and 9, respectively; those with polyhedral, rod-like, leaf-like, and tubular morphologies were obtained using the triblock copolymer P123-mediated hydrothermal strategy at pH = 1, 3, 6, 9, and 10, respectively.2. BiVO4 single-crystallites with rod-like, hollow spherical, spherical, and porous spherical morphologis were generated using NH3?H2O, NaOH, (NH2)2CO or NaHCO3 as base source for pH value regulation. The nature of alkaline source exerted an impact on the morphology of the final BiVO4 product. The samples obtained with P123 at pH = 3 and hydrothermal temperature = 80, 100, and 180 oC displayed a porous octapod-like, octapod-like, and polyhedral (major)/porous irregular octapod-like (minor) morphology, respectively. It is shown that the hydrothermal temperature influenced the morphology of the BiVO4.3. The as-fabricated BiVO4 samples exhibited different surface areas (0.3?11.8 m2/g), among which the one with a porous octapod-like morphology gave the highest surface area (11.8 m2/g). The estimated band gap energy (Eg) values of the monoclinic BiVO4 samples with multiple regular morphologies fell into the range of 2.22?2.44 eV. The porous octapod-like and rod-like counterparts possessed much lower Eg values (2.22?2.26 eV). Monoclinically crystallized porous octapod-like, rod-like, and tubular BiVO4 single-crystallites showed unusually high visible-light-driven catalytic performance for the degradation of MB in an aqueous solution under visible-light illumination, among which the one with a porous octapod-like morphology performed the best (total MB was degraded within 2 h of reaction). Such outstanding performance was attributed to its higher surface area, more oxygen defect amount, and unique particle morphology.4. Monoclinic BiVO4 single-crystallites with a flower-bundled morphology were generated and their Eg values were around 2.46 eV. Monoclinic BiVO4 single-crystallites with a porous hollow spherical morphology were obtained using a PVP (polyvinyl pyrrolidone)-assisted hydrothermal route with bismuth nitrate and sodium vanadate as metal sourse and urea as pH adjustor. When 1.25 g and 0.75 g of PVP were introduced, the diameters of the BiVO4 single-crystallites were 3?6 and 5?7μm, with the Eg values being 2.35 and 2.38 eV, respectively.
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