Fabrication And Photocatalytic Activity Study Of Conjugated Organic Polymer Poly ?Benzothiadiazole?/TiO₂ Composite

With the continuous development of society,the development and utilization of traditional fossil fuels can not meet the needs of sustainable development of society,and energy shortage and environmental pollution have threatened our life.Photocatalytic hydrogen evolution from water and pollutant removal using semiconductor photocatalysts under solar irradiation are an attractive proceess to alleviate the global engergy crisis and environmental pressure.Similar to many photocatalysts,TiO₂ is not efficient due to some shortcomings,such as narrow absorption ability.To overcome these drawbacks,and developping different semiconductor heterojunctions is an effective strategy to improve the photocatalytic efficiency.In this project,two conjugated organic polymers?COP?were designed based on the charge-tranfer processes of different semiconductor heterojuntion for photocatalytic reactions,and then COP-Ti O₂ with well band structure matching have been synthesized and characterized.It turns out that the COP-TiO₂ hybrid hetereojuctions have performed high photocatalytic activity.At first,the influence of electron-withdrawing or electron-rich units in the CMP on the bandgap or conduction-band?CB?/valence-band?VB?will be systematically studied.The contents of this paper are as follows:1.By means of in situ polymerization,the conjugated microporous polymer?benzothiadiazole??BBT?was used to modify the commercial semiconductor material TiO₂ to broaden its spectral absorption range and improve the photocatalytic activity.After optimizing the composition ratio,the resulting BBT-TiO₂ heterojunction exhibited dramatically enhanced visible-light-responsive photocatalytic activities??18.0 and 20.4 times higher activity for H2 evolution and ciprofloxacin degradation,respectively?as compared to BBT alone.Hydrogen generation efficiency remained stable within 8 hours,while the AQY value can reach 1.45%.Moreover,electron spin resonance?ESR?,cyclic voltammetry?CV?,fluorescence?PL?,active species capture,electrochemical impedance spectroscopy?EIS?and photocurrent were used to gain deep insight of the photocatalytic mechanism,and it is inferred that this heterojunction composites were common electron transfer mechanism.2.According to calculated HOMO and LUMO band position of polymer,a linear conjugated polymer PT was designed,and then nine kinds of PT-TiO₂ heterojunction composites with different PT contents were synthesized by in-situ polymerization.Photocatalytic experiments show that the photocatalytic performance of the composites increases first and then decreases with the increase of PT content.It was found that the heterojuncion withoptimizing the composition ratio exhibited dramatically enhanced visible-light-responsive photocatalytic activities??1.73 and 5.2?higher activity for H2 evolution and ciprofloxacin degradation,respectively as compared PT alone.Hydrogen generation efficiency remained stable within 25 hours,while the AQY value can reach 1.28% in the absence of Pt cocatalyst,which shows the superiority of PT-TiO₂ compared with BBT-TiO₂.