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.