Preparation And Visible Light Catalytic Properties Of Polyimide Composite Photocatalyst

Semiconductor photocatalysis technology is a kind of environmental protection technology to deal with environmental pollution,which has a very wide application prospect.Polymer semiconductors such as polyimide（PI）and carbon nitride（g-C₃N₄）can be used as photocatalysts to decompose water and degrade organic pollutants.However,the single phase semiconductor has many problems,such as wide band gap,low light energy utilization and serious photogenerated carrier recombination.Photocatalytic applications are limited.The method of semiconductor recombination can promote the separation of the hole pairs of photogenerated electrons prolongs the life of photogenerated carriers and improve the photocatalytic efficiency.The reduction performance of polyimide is poor when used as photocatalyst alone.In order to prepare high performance PI composites,the precursor of polyimide,polyamic acid（PAA）,was prepared by solution polymerization with PMDA and PDA as monomers and DMF as solvent.Soaked in acid copper solution,the Cu₂O/PI composite photocatalyst prepared by impregnation and heat treatment method after the carboxyl group on PAA was combined with Cu²⁺.The morphology and structure of the material were analyzed by EIS,XRD,SEM,DRS,Iph,TEM,FTIR,PL and XPS.The results shows that the uniform distribution of Cu₂O on the surface of PI increased the specific surface area of PI and provided more active sites,which greatly improved the photocatalytic performance.The constructed heterojunction significantly improves the absorption of visible light and the separation efficiency of photogenerated electron-hole pairs.The catalytic performance of the composite was investigated using p-nitrophenol as a simulated pollutant.To explore the best method by changing the preparation conditions,when the mass fraction of Cu₂O was 1%,the heat treatment temperature of 275℃,the heat treatment time is 2 h the catalyst has the best catalytic effect.The performance of Cu₂O/PI photocatalyst is good,stable and reliable through comparison of light and dark experiments and cycle experiments.Finally,the possible catalytic mechanism was speculated.To investigate the synergistic effect of PI and Cu₂O/g-C₃N₄,taking melamine as raw material,g-C₃N₄ was prepared by temperature rise method;PAA and copper acetate as raw materials,and finally Cu₂O/PI/g-C₃N₄ composite photocatalyst was prepared by impregnation and heat treatment method.By means of alternating current impedance（EIS）,fluorescence spectrum（PL）,photocurrent（IPH）and other methods,the doping of PI can significantly promote the separation of electron holes,which plays a synergistic role.When the mass fraction of PI and Cu₂O is 5%,the composite has the best catalytic effect.Using PAA and melamine as raw materials,PI/g-C₃N₄ composites were prepared by impregnation and heat treatment method.The morphology and structure of the material were analyzed by EIS,XRD,SEM,DRS,Iph,FTIR and PL.Rhodamine B was used as the simulated reactant to explore the catalytic performance.When the mass fraction of PI was 0.5%,it had the best catalytic effect,and the cycle experiment proved that it had good stability.