Preparation Of Graphite-phase Carbon Nitride Composite Materials And Their Photodegradation Performance

Graphite-phase carbon nitride nanosheet is one of the most popular materials in recent years.It has many excellent properties,such as a special structure similar to graphene,a suitable band gap for visible light absorption,no metal composition and the good stability,that it shows potential application value in many ways.Nevertheless,due to quite a few restrictions from its own structure and nature,there are some problems that inhibit its application in the photocatalytic field.For example,it absorbs the whole sunlight very weakly,the photogenerated electron-hole is easy to recombine,it tends to reunite like other nanoparticles and so on.In this paper,g-C₃N₄（s）was studied for modification regarding the above issue to prepare some composite photocatalytic materials,such as ZnO/g-C₃N₄（s）.C/g-C₃N₄（s）.TiO₂/g-C₃N₄（s）and N-TiO₂/g-C₃N₄（s）.The synthesized samples were characterized by FTIR,TGA,optical microscope,SEM,XRD,UV-VIS DRS,contact angle measuring instrument,photocatalytic reaction instrument and UV-visible spectrophotometer.First,the spinning solution containing Zn（Ac）₂ and a small amount of g-C₃N₄（s）was successfully spun to obtain PVP/Zn（Ac）₂/g-C₃N₄（s）composite fiber membrane when the PVP concentration was 12wt%.After the fiber membrane was calcined at high temperature,the remaining substance is confirmed to consist of g-C₃N₄ and ZnO according to FTIR,TGA and XRD.The SEM images show that g-C₃N₄（s）homogeneously dope into the ZnO fibers.The photocatalytic experiments demonstrate that ZnO/g-C₃N₄（s）composite fiber has higher activity than ZnO and g-C₃N₄（s）.Second,PAN fiber membranes were synthesized by electrospinning.G-C₃N₄（s）was successfully loaded onto the carbon fiber by suspended-drop and immersion method combined with high temperature carbonization process.FTIR and XRD patterns reveal that the synthesized material consists of g-C₃N₄ and C.The SEM photographs clearly show that g-C₃N₄（s）is loaded onto the surface of carbon fiber.The photocatalytic experiments demonstrate that C/g-C₃N₄（s）composite fibers which were synthesized under different carbonization temperature conditions have good adsorption properties.Particularly,the adsorption performance of the samples synthesized at 600℃ was the strongest.However,the photocatalytic performance of the composite fiber synthesized at 500℃ was the best.The activity of the sample after the composite modification was significantly improved compared with g-C₃N₄（s）.Third,TiO₂ fiber was synthesized by electrospinning and high temperature calcination.Then,the TiO₂/g-C₃N₄（s）composite was successfully prepared by monolayer dispersion method combined with heat treatment.FTIR spectra,TG curves and XRD patterns show that the composites contain g-C₃N₄（s）and TiO₂.SEM images show that g-C₃N₄（s）is tightly adhered to TiO₂ short fibers.The UV-Vis diffuse reflectance curves indicate that the composite has better absorbency.Photocatalytic experiments show that the photodegradation performance of composites was significantly improved compared with the pure TiO₂ and g-C₃N₄（s）under the simulated solar irradiation conditions and under the visible light irradiation conditions it was also improved slightly.Finally,in the case of melamine as a nitrogen source and pore former,N-TiO₂ fibers were synthesized by electrospinning combined with high-temperature calcinations.In addition,N-TiO₂/g-C₃N₄（s）composite was successfully prepared by monolayer dispersion method combined with heat treatment.FTIR spectra,TG curves and XRD patterns show that the composite consists of g-C₃N₄（s）and N-TiO₂.SEM photos show that N-TiO₂ which has a porous short fiber structure is tightly bound to g-C₃N₄（s）.Photocatalytic experiments show that the photocatalytic activity of N-TiO₂/g-C₃N₄（s）composite was significantly higher than that of pure N-TiO₂ and g-CaN4（s）under the simulated solar irradiation conditions and under the visible light irradiation conditions it was also enhanced.The porous N-TiO₂ fibers also exhibited some visible photodegradation properties,and the photodegradation performance was improved compared with the pure TiO₂.The results show that the porous structure,N-doping and semiconductor recombination can improve the photocatalytic performance.