Study On The Construction Of Heterojunction Of PDI Supramolecular Based Photocatalyst And Degradation Performance

Solar energy is a sustainable energy that has received much attention after rapid global development.Catalytic conversion of light energy through semiconductor materials is currently one of the most promising approaches to the current environmental crisis.After years of development,semiconductor photocatalytic materials have not only been confined to the field of inorganic materials,but research interest in organic catalytic materials has become increasingly intense.Organic semiconductor catalytic materials,such as porphyrins,phthalocya nine dyes,fullerenes,perylene derivatives,and graphite phase carbonitrides（g-C₃N₄）,etc.,which have excellent semiconductor behavior,thermal stability,and the self-assembly of ordered nanostructures has attracted more attention.Perylene imide（PDI）,as a typical perylene derivative,has a band gap of about 1.7 eV,is a typical n-type visible light-responsive photocatalyst,and its excellent physical and chemical properties make it excellent photocatalytic performance.However,for a sole PDI molecule,there are still many problems.At present,there are many researches on the performance improvement of PDI molecules,which mainly include group modification,the use of self-assembly characteristics to form supramolecules,the addition of cocatalysts,and the construction of heterojunction and so on.In this work,the effects of constructing Z-scheme WO₃@Cu@PDI supramolecular heterojunctions on degradation efficiency and the construction of photon carrier separation efficiency of n-n type CeO₂-PDI supramolecular heterojunctions during degradation were studied based on existing results and current hotspots.The main research is as follows:（1）Study on the construction of Z-scheme WO₃@Cu@PDI Supramolecular heterojunction and Its Degradation Performance.In this research work,WO₃@Cu was first prepared by photodeposition,and then the self-assembly characteristics of PDI were used to prepare WO₃@Cu@PDI supramolecular heterojunction.Experiments show that WO₃@Cu@PDI supramolecular has excellent light absorption ability and photocatalytic degradation activity.Under visible light conditions,the optimal WO₃@Cu@PDI supramolecular degradation efficiency of the tetracycline solution is 5times that of the PDI supramolecular and 40 times that of WO₃.At the same time,this study used XPS,XRD,SEM,TEM,PL,DRS,FTIR,EIS,and ESR to study the catalytic performance of the catalyst.Optical and electrochemical characterizations have demonstrated that the composite material has the strongest photo-generated carrier separation efficiency and low electron transfer resistance,which indicates the improvement of photo-generated carrier migration rate and separation efficiency.At the same time,through sacrificial agent experim ents and ESR characterization,the electron transport path in the Z-scheme system was confirmed,and the formation of Z-scheme heterojunctions enhanced the electron-hole separation enhancement.catalyst.（2）In this study,the self-assembly properties of PDI supramolecules were used to prepare the n-n type heterojunction CeO₂-PDI supramolecular heterojunctions and the reasons for their enhanced photocatalytic degradation activity were explored in detail.Through the construction of the heterojunction,a spec ific built-in electric field is formed between the two,and a specific electron transport channel is formed,thereby effectively accelerating the transfer of electron holes and thereby inhibiting the recombination of photo-generated carriers.Due to the high electron-hole separation efficiency of the composite,the photocatalytic degradation rate of the catalyst is 5.8 times that of pure PDI supramolecules,and 11.7 times that of pure CeO₂,and it has strong stability（after repeated reactions 3 times,it s till maintains over 80% of catalytic activity）.At the same time,this experiment explored the reasons for improving the photocatalytic performance of the catalyst by characterizing the materials by XRD,SEM,TEM,XPS,PL,DRS,EIS,photocurrent,and Mo tt-Schottky curves.The results show that the main reason that the nn-type heterojunction structure can greatly improve the photocatalytic degradation efficiency is that the built-in electric field formed in the heterojunction accelerates the migration of ele ctron holes generated by the material to a certain extent,which is effective to improve the separation efficiency of photo-generated electron-hole pairs.Therefore,the photo-generated carriers can be effectively migrated to the surface of the composite material,and the photocatalytic efficiency of the composite material can be effectively enhanced.