The Preparation And Pefrormance Of CuBi₂O₄-based P-n Heterojunction Visible-light Photocatalyst

Photocatalytic technology can decompose organic pollutants into H2O, CO2andother green small molecules under light, having advantages of high efficiency, energysaving, simple process and no secondary pollution, etc. The preparation and researchof photocatalyst plays a key part in the photocatalytic technology. In this thesis,copper bismuthate (CuBi2O4) complex oxides with a variety of novel morphologieshave been prepared via a low-temperature solution process. The structure,morphology and light absorption properties were characterized with XRD, SEM,TEM and UV–vis diffuse reflectance. The effects of synthetic conditions (treatmenttime, additives and KOH concentration) on the morphology have been discussed, andthe photocatalytic properties under UV–visible light irradiation were also evaluatedusing a degradation experiment. The results showed that the prepared samplesexhibited some novel morphologies, such as assembly nanorods, leaf-like nanosheetsand hierarchical nanoflowers, and excellent visible light absorption properties.Evident degradation for methylene blue was also observed in the range of UV–visiblelight irradiation with the help of a trace amount of hydrogen peroxide and theirphotocatalytic properties exhibited a strong dependence on morphology. Additionally,the photocatalytic mechanism was also illuminated.The prepared copper bismuthate (CuBi2O4) complex oxides with a variety ofnovel morphologies were also used as the catalysts in the preparation of1,4-butylacetylene glycol, the effect of morphology on the conversion rate was studied.The CuBi2O4/TiO2p-n heterojunction composites were obtained by in situsol–gel coating progress using prepared CuBi2O4powders and titania colloid. Theobtained CuBi2O4/TiO2composites were characterized by XRD, SEM, BET andUV–vis diffuse reflectance spectroscopy. Their photocatalytic and absorptionactivities were evaluated by the degradations of methyl orange and congo red under a500W xenon lamp and in the dark, respectively. Results showed that somecompositions of the prepared p–n heterojunction composites exhibited much higherphotocatalytic activity and absorption performance than pure CuBi2O4or pure TiO2, demonstrating that the formation of a p–n heterojunction between the two materialsplayed an important role in improving photocatalytic activity and adsorptionperformance. Absorption mechanism was also discussed from the viewpoint ofstructure.