Preparation And Characterization Of Bismuth - Based Semiconductor Photocatalyst

Since it was discovered that TiO2can be replied to degrade the pollutants in water, photocatalysis has become a hot subject to contribute to the environmental governance. To enhance the photocatalytic performance of TiO2, traditional methods were mainly concentrated on the modification of titanium dioxide. However, because of its large band gap (Eg=3.0-3.2eV), TiO2is only responsive to ultraviolet irradiation, which greatly limits its practical applications. It is expectative to develop novel photocatalysts with high photocatalytic activity under visible light. In this paper, the porous microsphere (β-Bi2O3was prepared by facile hydrothermal method, which has certain photocatalytic activity in visible light irradiation. And on this basis, the β-Bi2O3/Bi2O2CO3p-n and Fe-β-Bi2O3were prepared according to the compositing and doping to β-Bi2O3. Moreover, the photocatalytic performance of β-Bi2O3/Bi202CO3p-n and Fe-Bi2O3were carried out by degrading organic dye to study their photocatalytic mechanism. The main contents of this paper are as followings:1. The porous microsphere β-Bi2O3was synthesized by hydrothermal method with visible response. It was found that pH value affected the morphology of β-Bi2O3, so the finally pH value was chose to4.2according to related literature. The results from the photocatalytic experiment showed that the photocatalytic activity to degrade Cr(Ⅵ) could be enhanced by adding the phenol. Additionally, the MO also be degraded by β-Bi2O3to future study the photocatalytic performance.2. Novel porous β-Bi2O3/Bi2O2CO3p-n heterostructures with different contents of β-Bi2O3were synthesized by a simple thermodecomposition method with the temperture in the range of300-350℃. The crystalline phases of (β-Bi2O3and Bi2O2CO3both existed in the β-Bi2O3/Bi2O2CO3p-n heterostructures, which can be confirmed by XRD and TEM. Degradation of methylene organic (MO) was carried out to evaluate the photocatalytic activity of samples under visible light irradiation. β-Bi2O3/Bi2O2CO3heterostructure thermodecomposition at325℃presented the highest photocatalytic activity with24min irradiation time to degrade MO. The increased photocatalytic activity of β-Bi2O3/Bi2O2CO3could be attributed to the formation of the p-n heterojunction between P-Bi2O3and Bi2O2CO3, which suppresses the recombination of photoinduced electron-hole pairs.3. Fe-doped β-Bi2O3porous microspheres (Fe-Bi2O3) were fabricated by a facile hydrothermal method. The results from XRD analyses confirmed that a completed thermal conversion of the precursors to Fe doped β-Bi2O3at the temperature of375℃. The iron ions is substitution for Bi3+in the Bi2O3lattice structure with the presence of Fe3+, which can be proved by the XPS. According to the results of UV-vis spectra, the Fe-doped Bi2O3microspheres demonstrated a strong visible-light absorbance in the wavelength range of550-600nm. Under visible light irradiation (λ>420nm), Fe-doped photocatalysts with the content of4mol%displayed highest photocatalytic activity for the methyl orange (MO) photodegradation. An appropriate amount of Fe3+ions can act as intermediates for photo-generated holes and electrons transfer, which could enhance the lifetime of electrons and holes and reduce the e-/h+pair recombination rate.