Preparation, Characterization And Visible-Light-induced Catalytic Activities Of Bismuth Oxychloride/Bismuth Vanadium Tetraoxide With P-N Heterojunction Structure

A novel visible-light-active BiOCl/BiVO4photocatalyst with a p-n heterojunction structure was prepared using a hydrothermal method. The physicochemical properties of the as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis and UV-visible diffuse reflectance spectroscopy. The actual mole percentage of BiOCl in the heterojunction catalyst determined by the ion chromatography measurements was similar to that obtained using the method of Beer-Lambert law. The photocatalytic activity of the heterojunction was investigated by monitoring the change in methyl orange (MO) concentration under visible-light irradiation. The results reveal that the composite exhibited markedly improved efficiency for MO photodegradation in comparison with pure BiVO4, BiOCl, and Degussa P25. The highest activity was obtained in the BiOCl/BiVO4heterojunction using a composite of13mol%BiOCl and87mol%BiVO4. The molar ratio of BiVO4to BiOCl has a significant influence on the activity of the photocatalysts. When the system was irradiated with visible light for11h, the efficiency of the decomposition of MO with the most active0.75BiOCl/BiVO4heterojunction was85%, which is approximately3.54and1.89times greater than the decompositions obtained with pure BiVO4and commercially available Degussa P25, respectively. Moreover, the efficient visible radiation-activated BiOCl/BiVO4photocatalyst remained stable after five irradiation cycles. Enhancement of the decomposition of MO using BiOCl/BiVO4photocatalysts is attributed to the formation of B-type p-n heterojunctions between BiOCl and BiVO4, leading to an effective separation of photogenerated electrons and holes. Based on free-radical scavenging and N2-purging experiments, the photogenerated holes in the valence bands of BiOCl were demonstrated to be responsible for the direct oxidation of MO. The role of the photogenerated electrons in the conduction bands of BiVO4is to react with dissolved oxygen. Ultimately, with further improvement and optimization, the BiOCl/BiVO4heterojunction photocatalysts might be a viable alternative for photocatalytic applications.