The Preparation And Modification Of Bi-based Nanostruturs And Their Visible Light Photocatalytic Performances

With the rapid development of the human society,the energy crisis and environmental pollution are becoming more and more serious.Photocatalysis is considered to be one of the most effective ways to solve these two problems.TiO₂ is one of the most studied materials in numerous photocatalytic materials.However,due to the large band gap,TiO₂ is only active in UV region,which greatly limits its applications.Therefore,the development of novel visible-light photocatalyst is important and becomes a trend in the field of photocatalysis.Bi-based compounds with superior photocatalytic properities are important photocatalysts and have attracted much interests.In this work,three different Bi-based photocatalytic materials were synthesized by different methods,and the structures,morphologies and photocatalytic properties were studied.The main results are as follows:?1??-Bi₂O₃ nanopowders with high effective visible light photocatalytic properity were synthesized via a hydrolysis method combined with subsequent calcination,and the structure and morphology were charactetized through X-ray diffraction,scanning electron microscopy,high resolution transmission electron microscopy,X-ray photoelectron spectroscopy and ultraciolet-visible spectroscopy.The influences of the annealing temperature on the morphology,structure and photocatalytic performance were studied.The experiment results show that Bi₂O₃ powders synthesized by hydrolysis method directly possess low crystallization.When the calcaination temperature is 300?,Bi₂O₃ nanomaterials possess high crystallization and the self-assemblied thin sheets.When the calcination temperatures rise up,?-Bi₂O₃ will transform to ?-Bi₂O₃ with worse photocatalytic performances.The ?-Bi₂O₃ calcainated at 300? achieves the highest photocatalytic performances with degradation rate of 95% in 2 hours under visible light illumination.?2?BiOI nanosheets were synthesized by a hydrothermal method with the solvent of ethylene glycol,and Bi OI nanosheets were treated in thioacetamide?TAA?solution to synthesize Bi₂S₃/BiOI copmosites by a water bath method.The amount of Bi₂S₃ can be adjusted by changing the concentration of TAA solution.When the concentration of TAA solution is 2 mmol/L,Bi₂S₃/BiOI composites achieves the highest photocatalytic degradation rate,which can degradate MO solution completely in 2 h under visible light illumination.Compared with pure BiOI nanosheets,the photocatalytic performances were imporved greatly.The photocatalytic mechanism discussion shows that the special structure of Bi₂S₃/BiOI composites contributes to the separation of photogenerated electron-holes and reduce their recombination rate.?3?Hollow Bi₄Ti₃O₁₂ microspheres were synthesized via spray drying method combined with subsequent calcination.The structure and morphology of the products were characterized by different thermal analysis,X-ray diffraction,scanning electron microscope and ultraciolet-visible spectroscopy to optimize preparation process.The results show that hollow Bi₄Ti₃O₁₂ microspheres calcainated at 600? possess better crystallization and morphology.The photocatalytic performances were tested by degradating 20 mg/L MO solution under visible light and UV light illumination.Results show that Bi₄Ti₃O₁₂ microspheres possess high photocatalytic performances only in UV light illumination,and achieve the highest degradation rate at calcination temperature of 600?.