Synthesis And Photocatalytic Activity Of Novel Bismuth Oxide-based Heterojunction Catalysts

Bismuth-based compound such as Bi₂O₃ has received considerable attention in near one decade as a potential visible light-driven photocatalyst due to its narrow band gap,high oxidation power of holes in valence band,nontoxicity and stability.However,the absorption edge of Bi₂O₃ only locates at 450nm and the recombination possibility of light-generated electrons and holes is relatively high,which are directly affected its photocatalytic activity.A strategy to improve the separation efficiency of electron-hole pairs is to couple the semiconductor with another semiconductor to form heterojunction at their interface.Therefore,in order to improve separation efficiency of light-generated electron-hole pairs in Bi₂O₃ and extended its response to visible light,novel Fe VO₄/Bi₂O₃ and Au/FeVO₄/Bi₂O₃ photocatalysts were designed and prepared.And their photocatalytic activities and mechanisms were studied systematically.Firstly,a novel Fe VO₄/Bi₂O₃ heterojunction photocatalyst was successfully synthesized.The catalysts were characterized by XRD,TEM,Uv-vis DRS and PL.Its photocatalytic mechanism was discussed.The results showed that FeVO₄/Bi₂O₃photocatalyst improved the photocatalytic activity by 29%and 20%as compared with that of FeVO₄ and Bi₂O₃ for degradation of malachite green under visible light illumination.The enhancement of the photocatalytic activity of the FeVO₄/Bi₂O₃heterojunction catalysts can be ascribed to the reduced recombination of the electron-hole pairs in the photocatalytic reaction.In order to confirm that the Au can be loaded on the catalyst by photo-deposition method and investigate the photocatalytic performance of Au/Bi₂O₃,the Au/Bi₂O₃catalyst was prepared by photodeposition method.The detailed information about the morphology of Au/Bi₂O₃ was investigated with TEM.The results showed that some4-5nm gold nanoparticles were dispersed in the Bi₂O₃ particles.Malachite green photocatalytic degradation experiments demonstrated that Au/Bi₂O₃ samples had good photocatalytic activities under visible light irradiation.The reason for the enhanced photocatalytic activity was the Au loaded on the Bi₂O₃,which leaded to the higher separation efficiency of electron-hole pairs and the enhancement in light absorption by the plasmon resonance effect of Au.TheAu/FeVO₄/Bi₂O₃heterojunctionphotocatalystwaspreparedby photodeposition method.The crystalline structure,light absorption performance,separation of light-generated eletrons and holes and photocatalytic activity of the Au/FeVO₄/Bi₂O₃ heterojunction photocatalyst were investigated and the results showed that the Au/Fe VO₄/Bi₂O₃ heterojunction photocatalyst exhibited higher photocatalytic activity than the FeVO₄/Bi₂O₃ for the degradation of malachite green undervisiblelightillumination.Thephotocatalyticmechanismofthe Au/FeVO₄/Bi₂O₃ was also proposed.In short,the present work overcomes the low photocatalytic efficiency of Bi₂O₃photocatalyst which caused by the recombination of photogenerated electron hole and its narrow band gap.In addition,this work provides a new way to design the novel bismuth based heterojunction photocatalyst.