Study On Synthesis Of Supported Carbon Nitride-based Photocatalytic Materials Based On Photonics Film And Its Performance

Azo organic synthetic dyes,which are widely used in the textile printing and dyeing industry,are difficult to degrade and have"three causes"characteristics,causing various pollution problems to be solved urgently.Semiconductor photocatalysis technology has attracted widespread attention as a"green technology"to solve environmental energy problems in recent years.As a new type of visible-light responsive non-metal semiconductor photocatalyst,graphite carbon nitride（g-C₃N₄）has attracted attention due to its advantages such as simple synthesis,unique and adjustable electronic band structure,and low cost and easy availability.However,the eigenstate g-C₃N₄ has a wide band gap（～2.7 e V）,only responds to the blue-violet light region in the solar spectrum,high photo-generated carrier recombination rate and poor conductive,which greatly limits its photocatalytic performance.In addition,the photocatalyst powder has problems such as large amount of consumables and difficult separation and recovery,which also limits its practical application.Therefore,to further optimize the visible light response and conductivity of g-C₃N₄,and to develop a supported carbon nitride system at the same time will help promote its further application in actual environmental treatment.In this paper,based on the polycaprolactone（PCL）photonics film,a preliminary study on the membrane loading of g-C₃N₄ was carried out.At the same time,the conductive polymer polyaniline（PANI）was introduced by in-situ polymerization to improve the conductivity of g-C₃N₄ and to establish a composite photocatalytic film system at the same time,which provides a certain theoretical basis for the practical application of g-C₃N₄.First,urea is used as the nitrogen-rich precursor,and the cheap and non-toxic calcium acetylacetonate（CAA）material is selected as the organic co-monomer for the first time to prepare the new carbon nitride photocatalyst（CN/CAA）co-modified by Ca²⁺and HDMP groups by copolymerization strategy.The results show that the doping amount of CAA is an important factor for modification,and the photocatalytic methyl orange（MO）degradation activity of the modified sample CN/CAA-15 with the optimized doping concentration（15 g/L）was 2.92 times higher than that of the pristinel g-C₃N₄.A small amount of CAA doping does not change the characteristic morphology and structure of the pristine g-C₃N₄,but the co-modification of Ca²⁺and HDMP group is helpful to improve the electronic density and adjust the electronic structure,which makes theπ-conjugated system is effectively expanded and the optical absorption capacity of the whole spectrum is effectively improved.The recombination of photo-generated carrier effectively has been suppressed,and the separation and migration capabilities are improved but the conductivity is still low.The mechanism analysis shows that the degradation of MO on CN/CAA is mainly due to the photoreduction process caused by photogenerated electrons and the negative shift of conduction band position makes the conduction band electrons have stronger photoreduction ability.Secondly,the ordered porous film obtained by selecting PCL as the film-forming material has better strength and hydrophilicity,and is suitable as a photocatalyst carrier.A simple and environmentally friendly solvent evaporation self-organization method is used to prepare ordered porous photonic films,with high molecular organic polymers polystyrene（PS）and PCL as the main film-forming materials,the influence of the film-forming system and environment on the pore size and order of the photonics film is studied.Finally,the PANI@PCL composite film was prepared by in-situ polymerization,and CN/CAA-15 catalyst sample was added to prepare the supported carbon nitride composite photocatalytic film（CN/CAA-PANI@PCL）based on PCL photonics film.The results showed that:The CN/CAA-PANI@PCL3 photocatalytic film sample polymerized for 3 hours retained the porous structure of the PCL film.The PANI nano-particles mainly grew on the inner wall of the pore or embedded in the hole,while CN/CAA-15 is mainly compounded on the surface.Compared with CN/CAA-15 photocatalyst sample,the charge transfer resistance of composite photocatalyst（CN/CAA-PANI3）is significantly reduced,and the photocurrent response value is increased 6 times.Too long polymerization time will make PANI to overgrow to cover the pore structure and carbon nitride sheet layer,and then affect the charge separation and migration.The composite photocatalytic film material has good photocatalytic activity and stability,which the carbon nitride material plays a major role in the photocatalytic reaction process in the system.Mechanism analysis:On the one hand,the favorable porous structure of the film carrier provides more reactive sites;on the other hand,the type-II heterojunction constructed by PANI and CN/CAA-15 promotes the rapid electron transfer and efficient separation of electron-hole pairs in the composite carbon nitride material CN/CAA-PANI,resulting in significantly enhanced photoelectrochemical performance and good photocatalytic activity.In summary,the modified graphite phase carbon nitride prepared by Urea/CAA co-polymerization has excellent visible-light response and photocatalytic activity.The supported carbon nitride photocatalytic film system is prepared by using photonic film with good performance and simple preparation as a porous film substrate.The thin film system will provide new ideas for further improving the feasibility of g-C₃N₄ in the practical application of photocatalysis.