Study On Preparation And Degradation Performance Of Titanium Dioxide-based Photocatalyst

Photocatalytic technology has broad prospects in the degradation of organic pollutants due to its environmental protection,energy saving a nd high efficiency.As the earliest discovered photocatalyst,TiO₂ is widely concerned due to its low cost,strong oxidizing ability,and stable physical and chemical properties.However,TiO ₂has a wide band gap and can almost only absorb ultraviolet ligh t,and photo-generated electrons and holes are easy to recombine.These shortcomings limit the application of TiO₂.In this paper,in order to broaden the light response range to visible light and enhance the separation efficiency of photogenerated electro ns and holes,solvothermal method was used to prepare TiO₂,which is an economical and efficient method to modify TiO₂.And Bi₂WO₆ was used to construct a heterostructure to prepared photocatalyst which has good photocatalytic performance under visible lig ht.We have explored its ability to degrade organic dyes and antibiotics,and analyzed the photocatalytic mechanism.The main research contents were as follows:（1）Carbon quantum dots（CQDs）with up-conversion luminescence were prepared via reflux method by using olive leaf as the carbon source,and CQDs/TiO ₂were prepared by the hydrothermal method,and the effect of the loading of CQDs on the photocatalytic performance was also explored.The crystal structure,composition and morphology of the samples were analyzed by using XRD,XPS,SEM,TEM and UV-vis DRS.Tetracycline（TC）and Rhodamine B（Rh B）were used as simulated pollutants to evaluate the degradation performance of the photocatalyst.The results showed that the prepared CQDs had an average size of 1.1 nm,good dispersibility,and were uniformly supported on the surface of TiO₂.When irradiated under visible light for 10 min and 70 min,the degradation rates of 5%CQDs/TiO ₂ on TC and Rh B reached81%and 92%,respectively.After 5 times of recycling,the degradation performance did not change significantly.Photocurrent and PL tests showed that the loading of CQDs can improve the separation efficiency of TiO ₂ photogenerated carriers.Combined with the up-conversion luminescence performance of CQDs,UV-vis DRS and radical trapping experiments of the photocatalyst,the photocatalytic mechanism was analyzed.（2）The Bi₂WO₆/CQDs/TiO₂ composite photocatalyst was prepared by hydrothermal method,and the influence of CQDs loading on the degradation performance of the composite photocatalyst was explored.The crystal structure,composition and morphology of the photocatalyst were analyzed by XRD,SEM and TEM.The results showed that the degradation rate of Rh B by the composite photocatalyst could reach 92%when irradiated under visible light for 70 min at the loading of CQDs was 0.5%.UV-vis DRS,photocurrent and PL analysis results show ed that,compared with Bi₂WO₆ and 0.5%CQDs/TiO₂,Bi₂WO₆/CQDs/TiO₂-0.5 had better visible light response,higher photogenerated carrier separation efficiency,and more excellent photocatalytic degradation performance.（3）Bi₂WO₆/TiO₂ heterojunction was constructed by hydrothermal method.And the crystal structure,morphology and photocatalytic degradation performance of the composite photocatalyst with different molar ratios of TiO ₂ and Bi₂WO₆ were studied.The results showed that when the molar ratio of TiO₂ and Bi₂WO₆ was 6∶1,the composite photocatalyst has the best degradation performance.The degradation rates of TC and Rh B were 78%and 96%when irradiated under visible light for 25 min and20 min,respectively.PL and photocurrent analysis results showed that the combination of TiO₂ and Bi₂WO₆ can significantly improve the photo-generated carrier separation efficiency of the composite photocatalyst.Finally,the photocatalytic mechanism of Bi₂WO₆/TiO₂ was analyzed.