| Semiconductor photocatalysts have attracted considerable attention due to their strong photocatalytic effect on the decomposition of dye pollutants, the research on visiblelight-driven photocatalysts has important academic significance and practical value.In this paper, BiVO4and Ag/BiVO4composite photocatalysts were synthesized and characterized. The photocatalytic performance of the as-prepared samples were evaluated by decomposition of rhodamine B(RhB) under visible light irradiation. Study on the effects of pH on bismuth vanadate prepared by hydrothermal method and the optimum content of the doped Ag. Additionally, the mechanism of enhanced photocatalytic activities of Ag/BiVO4sample and the Solar photocatalytic oxidation were also discussed.The main points of this thesis are summarized as follows:1) Bismuth vanadate (BiVO4) powders were synthesized using the hydrothermal strategy with bismuth nitrate and ammonium metavanadate as inorganic sources, NaOH for pH adjustment. The materials were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and UV-vis diffuse reflectance spectra techniques(UV-vis DRS). It revealed that the pH values of the precursors can influence significantly on the particle structures and morphologies of the BiVO4products.When the pH value of the precursors controled at1.9, the prepared sample is tetragonal erystal structure(t-BiVO4),others all are monoelinic structure(m-BiVO4). Comparison of the m-BiVO4and t-BiVO4on the ability of light absorption, the DRS spectra reflected that m-BiVO4showed higher light absorption than that of t-BiVO4.The decomposition of RhB in aqueous solution under visible light (λ>420nm) irradiation and variation of TOC concentration were evaluated. The results showed that photocatalytic activities of BiVO4samples prepared at different pHs varies greatly, and the optimum pH value was about6.7, which photodegradation rate could be up to95.3%in240min. the reduction of TOC concentration in the degradation of RhB indicated that the mineralization of RhB occurred. Additionally, the relationship between the phase, morphology of photocatalysts and their photocatalytic activities were also discussed.2) Ag/BiVO4composite photocatalysts were synthesized via a facile hydrothermal method without adding any surfactant. The as-prepared samples were characterized by XRD. SEM, XPS and UV-vis DRS techniques. The results indicated that the doped Ag species greatly improved morphologies and structures performance of the synthesized composites. The DRS spectra reflected a red-shifted trend of absorption band after Ag species doped BiVO4. The photocatalytic activities of the Ag/BiVO4composite photocatalysts were evaluated by the decomposition of RhB in aqueous solution under visible light irradiation. It revealed that Ag/BiVO4photocatalysts exhibited superior performance and the optimum content of the doped Ag can be easily controlled by adjusting the ratio of the rare precursor.3) The reactive species trapping experiments were designed to investigate the main reactive oxygen species in the photocatalytic process of10wt%Ag/BiVO4.Three kinds of scavengers, including Isopropanol, benzoquinone and EDTA were employed to investigate their indirect effects, respectively. The results of the experiments indicated that the decomposition of RhB is mainly explained by the participation of holes and by the contribution of superoxide anions to a lesser extent. Additionally, the mechanism of enhanced photocatalytic activities of Ag/BiVO4sample was also discussed in this paper.4) The photocatalytic degradation of RhB in solar irradiat ing with BiVO4and Ag/BiVO4suspension was investigated. The results showed that the degradation of organic pollutants under sun light irradiation in photocatalyst driven is feasible. |
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