Study On Preparation And Photocatalytic Of Graphite Phase Carbon Nitride Composite Materials

The two major problems that people urgently need to solve now are environmental pollution and energy crisis.The emergence of semiconductor photocatalysis technology can effectively reduce environmental pressure.This technology can not only use solar energy to deal with environmental pollution,but also can convert solar energy into fuel.Therefore,this technology is also known as the green technology to solve energy shortage and environmental pollution.At present,there are many types of photocatalytic materials studied,but there are still no materials that can meet the requirements of stable,efficient and wide spectrum absorption,so this field has been widely concerned.Graphite phase carbon nitride（g-C₃N₄）is a nonmetallic organic polymer semiconductor,Because of its chemical stability,thermal stability,semiconductor properties,and when the band gap width of 2.7 ev,as well as the appropriate valence band（VB,1.4 ev）and conduction band（CB,1.3 ev）locations.And the preparation of raw materials is easy to obtain and simple method,in the field of photocatalysis has been widely concerned.However,there are still some disadvantages for practical applications:1.Absorption of blue-violet light with wavelength less than475 nm in the solar spectrum;2.Its own light absorption andπ-electron conjugation effect make the photocatalytic activity low;3.The smaller surface area provides less active sites,thus causing photogenerated electrons and holes to easily recombine.Therefore,this paper is dedicated to study on appropriate modification of g-C₃N₄’s photocatalytic defects and enhancement of photocatalytic activity.The specific contents are as follows:（1）Melamine and cyanuric chloride are used as raw materials to prepare a series of F-g-C₃N₄ with different precursor ratios by thermal polymerization.The results of XRD and FT-IR showed that the F-g-C₃N₄ structural unit was composed of three triazine rings.The morphology of F-g-C₃N₄ was auricular by SEM.The specific surface area of F-g-C₃N₄ prepared by this method was 156.2 m²·g^-1,greater than g-C₃N₄-MA prepared by melamine thermal polymerization.When the mass ratio of cyanuric chloride to melamine is 4:2（F-g-C₃N₄-5）,the photocatalytic degradation of rhodamine B is the highest with visible light irradiation,and the degradation rate is 99.62%.The photocatalytic mechanism capture study found that in the photocatalytic reaction process of F-g-C₃N₄-5 photocatalytic system,the order of active species is·O₂^->h⁺>·OH.（2）A series of g-C₃N₄/PGS composites were prepared by one-step thermal polymerization use melamine,cyanuric chloride and palygorskite as raw materials.The structure,morphology,specific surface area and optical properties of the composites were characterized by XRD,FTIR,SEM,N₂-adsorption desorption,Uv-dis and PL.Under visible light irradiation,the composite material was used as photocatalyst.When the PGS content in the composite material was 20%,30 mg g-C₃N₄/PGS photocatalytic degradation of 30 mL 20 mg/L methylene blue was better,and the decolorization rate was 96.95%.During the photocatalytic degradation process,·OH is the main active group.（3）g-C₃N₄ and rGO g-C₃N₄/rGO composites were prepared by thermal polymerization use melamine,cyanuric chloride and graphene as raw materials.The photocatalytic properties of g-C₃N₄/rGO under visible light irradiation were investigated with Rhodamine B as the targeting molecule.The experimental results show that the composite has a higher photodegradation effect on Rhodamine B.When the amount of graphene added is 1:8 with g-C₃N₄,the photodegradation rate of rhodamine B is 96%when the light is exposed for 30 min.After the hydrophilic treatment of the composite material,the photodegradation rate of rhodamine B was97%,and the photocatalytic activity group was·O₂^-.