Study On Preparation And Properties Of Vanadium Based Compounds And Their Composites

In recent years,environmental pollution and energy crisis caused by fossil combustion have become increasingly urgent.Photocatalytic reaction,as an application of converting solar energy into chemical energy,has become a hot topic.Scientists from all over the world focus on the development of new photocatalytic materials and the study of photocatalytic principle.The development of efficient and stable photocatalysts is a major challenge worldwide.Vanadium-based compounds have been paid close attention by scientists because of their excellent photocatalytic properties,rich chemical structures and excellent kinetic properties.In this thesis,two vanadium compounds,Zn₃V₂O₇(OH)₂·2H₂O and BiVO₄,were synthesized by hydrothermal method,surface deposition and photoreduction techniques,while their composite materials were designed and prepared.Their structure and photocatalytic performance were investigated.Specific research contents are as follows:(1)Zn₃V₂O₇(OH)₂·2H₂O nanostructures with various morphologies were prepared by hydrothermalmethod.TheZ-schemecompositephotocatalyst Ag/Ag Br/Zn₃V₂O₇(OH)₂·2H₂O was successfully prepared by surface deposition and subsequent photoreduction using flower-like Zn₃V₂O₇(OH)₂·2H₂O as support.The prepared3D flower-like Ag/Ag Br/Zn₃V₂O₇(OH)₂·2H₂O composite has a larger specific surface area and a wider visible light response range.The composite photocatalyst has excellent photocatalytic degradation activity with the degradation efficiency for MB is about 98.8%in100 min.The excellent photocatalytic activity is attributed to the intermediate‘bridge'effect of Ag nanoparticles.(2)BiVO₄ nanoparticles and BiVO₄/rGO composites were prepared by hydrothermal method.In the experiment,EDTA-2Na was used to provide an acidic environment to prevent the hydrolysis of Bi³⁺,instead of inorganic acids in the traditional preparation process.EDTA-2Na also acted as a surfactant.The excellent conductivity of rGO greatly improve the separation efficiency of photogenerated carriers in the composites,and enhence the photocatalytic activity of the material.The degradation efficiency of BiVO₄/RGO-6-30 for organic pollutants Rh B reached 98.3%in 180 min.(3)The Z-scheme composite photocatalyst BiVO₄/g-C₃N₄ composite photocatalyst were successfully obtained by hydrothermal method.The BiVO₄/g-C₃N₄ composite material has a large specific surface area of 91.5 m²/g,and has a strong absorb ability of visible light.The composite photocatalyst showed excellent photocatalytic activity under visible light,and the degradation efficiency of BiVO₄/g-C₃N₄-30%for organic pollutants Rh B reached 95%in 160 min.