Synthesis And Photocatalytic Activities Of Bismuth-based Composite Oxide-based Nanomaterials

The rapid development of modern industrial civilization makes people's material life more and more abundant.However,industrialization makes fossil fuels exploited and used in large quantities,which not only causes the exhaustion of resources,but also destroys the environment.Deteriorating environmental pollution and energy shortages have raised awareness of potential global crises.For the sustainable development of human society,the development and utilization of renewable green energy and the solution of environmental pollution have become a major issue facing human society.Among the various ongoing projects,photocatalytic technology is considered to be one of the most promising technologies,characterized by the direct use of renewable,cheap and abundant solar energy.Photocatalyst is a key part of this technology.So far,many efforts have been devoted to the design and synthesis of catalysts with strong absorption and utilization of broad-spectrum solar energy,high separation efficiency of electrons and holes,and energy bands suitable for redox reaction.Bismuth-based composite oxides have attracted much attention as a new type of photocatalytic materials because of their unique layered structure and attractive energy band structure,which have strong light response ability.It has good application prospects in the field of photocatalysis and attracts the attention of many researchers.In this paper,three kinds of Semiconductor Photocatalysts based on bismuth-based composite oxides were constructed,and their photocatalytic properties were studied.At the same time,the reaction mechanism of different systems was studied in depth.The specific work is as follows:(1)Rare earth doped BiYO₃ nanotubes were prepared by a simple and economical electrospinning technology combined with calcination at different temperatures.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),EDS element analysis,X-ray photoelectron spectroscopy(XPS),ultraviolet-visible diffuse reflectance spectroscopy(UV-Vis DRS)and electrochemical impedance spectroscopy(EIS)were used to characterize the crystal structure,morphology,adsorption and photocatalytic mechanism of the synthesized samples.The average diameter of nanotubes is about 100 nm.They exhibit enhanced visible light-driven photocatalytic decomposition of Congo red.The results show that the photocatalytic activity of the samples calcined at 700 C is the highest.Different rare earth doping can improve the adsorption and photocatalytic activity of the materials,which may be related to the formation of impurity energy levels.Among them,the Nd-doped BiYO3 sample has the best photocatalytic activity in visible light degradation of Congo Red.(2)A novel heterojunction Bi₄O₅I₂ flower/Bi₂S₃ nanorod was prepared by solvothermal method combined with anion exchange process.In-situ growth of Bi₂S₃nanorods from Bi₄O₅I₂ nanosheets means that there is a strong coupling and intimate interface between the two semiconductors.The tunable morphology,composition and optical properties of Bi₄O₅I₂/Bi₂S₃ heterostructures with different reaction times were characterized in detail.The photocatalytic reduction of Cr(VI)was evaluated under visible light irradiation(?>420 nm).The results show that Bi₄O₅I₂/Bi₂S₃ heterojunction has good photocatalytic activity and stability.The maximum apparent rate constant can reach0.05614 min^-1,which is 56 times and 7.5 times of the original Bi₄O₅I₂ and Bi₂S₃.Further detailed characterization shows that the large amount of adsorption and stable reduction of Cr(VI)can be attributed to the effective transfer of photogenerated carriers and spatial separation.(3)BiVO₄/Bi₂O₃ composites were synthesized by one-step solvothermal method.By controlling the proportion of Bi(NO₃)₃·5H₂O and NH₄VO₃,a series of BiVO₄/Bi₂O₃Composite Semiconductor Photocatalysts with different proportions were successfully synthesized by solvothermal method,and the samples were characterized in detail by the related characterization methods.Finally,the photocatalytic performance of the catalyst for NO removal was tested,and the photocatalytic mechanism was discussed with the related characterization.The results show that BVO-5(Bi:V=1.2:1)has the best photocatalytic activity for NO removal and has a certain stability.Further detailed characterization showed that the p-n junction formed in the composite could promote the transfer of photogenerated carriers and inhibit their recombination,thus improving the photocatalytic performance of NO removal.