Preparation And Properties Of Perylene Diimide /CuS/cotton Photocatalytic Materials

At present,the economic growth model brought about by resource consumption has brought serious pollution problems.Water pollution problems represented by dyeing wastewater and antibiotic wastewater have become a serious challenge to human sustainable development.Exploring advanced,low-cost and efficient Sewage treatment technology has become a hot spot in research.The emergence of semiconductor photocatalysis technology has opened up a new way for wastewater treatment,but common semiconductor materials such as Ti O₂ or Ag-based materials have their own limitations such as poor visible light response or poor stability,so the development of new types with strong light absorption capacity and stability The semiconductor materials have become the focus of research.Perylene diimide（PDI）,as a new type of organic semiconductor material,has super light absorption capacity,adjustable energy level and excellent stability,so it has outstanding advantages in the field of photocatalysis.However,the catalytic performance of PDI also has limitations.Therefore,in this study,the PDI/Cu S composite photocatalytic material was constructed by self-assembly and heterojunction modification,which can improve catalytic performance.In addition,to overcome the problem of easy aggregation of powder catalysts,photocatalytic function cotton fabrics are also prepared through electrostatic self-assembly methods.The work of the paper is as follows:Firstly,the PDI/Cu S supramolecular heterojunction was prepared through a two-step self-assembly method:PDI molecules were used as precursors to self-assemble to form PDI supramolecular materials through intermolecular forces（hydrogen bonding,π-πconjugate）.Subsequently,nano-Cu S was introduced into the PDI supramolecular structure through electrostatic self-assembly and in-situ reduction methods to obtain the PDI/Cu S supramolecular heterojunction.During the synthesis process,the degradation experiment of RB-19 dye and tetracycline was used as a reference to optimize the synthesis.It is found that when the p H of the PDI monomer self-assembly is 3,the time is 4 h,the proportion of Cu S in the composite system is 10%,the synthesis temperature of the composite system is 60℃and the time is 4 h,the PDI/Cu S prepared has the highest activity.In addition,performance characterization of the composite catalyst:Uv-visible spectroscopy,XRD,XPS,Raman spectroscopy and other characterizations have proved that theπ-πstacking type of PDI supramolecular materials is H-type,and PDI/Cu S has better characteristics than self-assembled PDI.The large degree ofπ-πstacking is conducive to the rapid migration of photogenerated electrons between PDI molecules and the interface with Cu S.In order to further verify the migration of photogenerated electrons,the electrochemical properties of the material were characterized.The results of PL,EIS and transient photocurrent all proved the rapid separation of electrons and holes,which undoubtedly overcomes the inherent defects of PDI molecules.The catalytic performance research experiment undoubtedly verified the above results.The degradation rate for dyes of PDI/Cu S is 11 times than that of Cu S and 3.3 times than that of self-assembled PDI;Furthermore,the catalytic performance is the degradation rate for TC of Cu S is 6 times and 2.6times than that of self-assembled PDI.And it can still maintain high activity under simulated actual application conditions,which illustrates the success of the modification and its potential application value.The process of the catalytic decomposition of pollutants and the exploration of possible photocatalytic mechanism:First,according to the ESR test and the active substance capture experiment,it is verified that the active species in the degradation process are mainly h⁺and·O^2-.Then based on the position of the VB and CB obtained by the Mott-Schottk curve,a photocatalytic mechanism based on pn-type heterojunction is proposed,which includes the formation of a built-in electric field and electrons and holes rely on the built-in electric field and energy range.The role of the rapid migration between the interface,effectively reducing the recombination,played a vital role in catalysis.Finally,using three-dimensional fluorescence and LC-MS to explore the decomposition process of tetracycline,demonstrated the change process of tetracycline from macromolecular pollutants to small molecular substances under the action of holes and superoxide ions.Finally,preparation and characterization of photocatalytic function cotton fabric:in order to overcome the defects of powder catalyst,the PDI/Cu S composite system was fixed on the cationic modified cotton fabric by electrostatic adsorption to achieve the purpose of simple recovery and recycling.Five cycles of experiments were performed on cotton fabrics,and it was found that the degradation rate of more than 70%can still be maintained after the cycle,and the morphology of the fibers will not change before and after the cycle,which shows the excellent recycling ability and stability of the system.