| BiVO4 (Bismuth vanadate), a novel semiconductor photocatalyst, has attracted much attention due to its promising application in the fields of solar energy transformation and photodegradation of contaminant under visible light. However, the photocatalytic activity of pure BiVO4 is relatively low due to its high recombination rates of photoinduced electron-hole pairs. Nowdays, much works have been done in order to enhance its photocatalytic performance. In this study, RGO, Bi2WO6, Co(NO3)2ยท6H2O and NH4F were selected to modified BiVO4, respectively. The BiVO4-based composites were mainly synthesized by the hydrothermal method. The photocatalytic experiments showed that photocatalytic properties of the composites were improved with different degree as compared to the pure BiVO4. The mechanism of the enhanced photocatalytic activity was also discussed. The main contents are as follows:1. Reduced graphene oxide/BiVO4 (RGO/BiVO4) photocatalysts were prepared by a hydrothermal process using ethylene diamine tetraacetic acid (EDTA) as chelating agent. The as-prepared samples were characterized by XRD, FE-SEM, FT-IR and DRS. The results indicated that GO were reduced into RGO during hydrothermal process and the visible-light photocatalytic activity of BiVO4 is enhanced in the presence of RGO which did not change the crystalline of BiVO4. The RGO/BiVO4 with graphene oxide (GO) of 15.0%(in mass) exhibited a superior photocatalytic activity. The recombination rate of the photo-generated electron-hole decreased owing to the excellent electron transport ability of RGO and the light absorption intensity was strengthened, thus the photocatalytic activity.2. BiVO4 were fabricated by precipitation process, and BiVO4/Bi2WO6 composite photocatalysts were synthesized by coupling a homogeneous precipitation method with hydrothermal techniques. The as-prepared samples were characterized by XRD, FT-IR, SEM, EDS, DRS and PL, respectively. The results revealed that BiVO4/Bi2WO6 composites exhibit higher photocatalytic activities than either pure Bi2WO6 or BiVO4. The enhancement of photocatalytic activity was attributed to the improvement of light absorption, the excellent adsorbability, the narrow band gap and increasing separation rate of photo-generated charge carriers.3. A series of Cobalt doping BiV04 composites (Co/BiVO4) were successfully synthesized by a hydrothermal method using ethylene diamine tetraacetic acid (EDTA) as chelating agent and Co(N03)2 as raw material. XRD, EDS and TEM indicated that Co species were successfully doped into the BiVO4. According to the XPS analysis, the loaded Co was in the state of Co3O4. The addition of Co significantly improved the photocatalytic performance of BiVO4 under visible light irradiation. The enhancement of photocatalytic performance of Co/BiVO4 composite photocatalysts was because of the improvement of light absorption, the excellent adsorbability, the narrower band gap and the higher separation efficiency of photo-induced charges.4. Using NH4F as the source of nitrogen and fluorine, N-F codoped BiVO4 visible light driven photocatalysts (N-F/BiV04) have been synthesized via a hydrothermal method. The resulting materials were characterized by a series of techniques, and the results showed that the N-F/BiVO4 photocatalysts exhibited a little higher photocatalytic activity for MB degradation under visible light irradiation compared with pure BiVO4. It was revealed that N atoms replaced the common oxygen in the crystal lattice of BiVO4 to form the O-Bi-N-V-O bond while only there were the adsorbed fluoride species on the surfaces of the samples. The enhanced photocatalystic activity of N-F co-doped BiVO4 was due to the alteration of the surface acidity or basicity, more oxygen vacancies and narrower band gap energy. However, N-F co-doping can not effectively inhibit the recombination of the photo-induced carriers, thus the improvement of photocatalytic activity was not obvious. |
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