Preparation And Photocatalytic Properties Of Two Dimensional Carbon Nitride-based Composites

As some of the traditional non-renewable energy materials,such as coal,oil and natural gas,have been gradually exhausted,the environmental pollution serious increasingly.It is an important task to develop some green environmental protection energy materials in modern society.Solar energy,as one of a new type energy source,possesses many advantages,such as safety,green,low cost,wide source,and no environmental constraints.Thus,a quantity of scientists dedicated to convert solar energy to the demanded energy for the human society to effectively solve the energy shortage and environmental pollution.Semiconductor photocatalytic materials are under the action of light,so as to achieve degradation of organic pollutants or chemical reactions between water decomposition to produce hydrogen and other purposes.Among them,graphite carbon nitride?g-C₃N₄?is a highly efficient visible-light-responds semiconductor due to its proper band structure,thermal stability and chemical stability.It has been considered to have wide application prospect in the field of photocatalysis.However,the photogenerated electron-hole pairs of g-C₃N₄ usually suffer from serious recombination.Therefore,it is highly desirable to find ways to improve the photocatalytic performance of g-C₃N₄.In the past research,the structure modification,element doping,copolymerization,as well as the formation of the g-C₃N₄-based semiconductor materials and other methods were used to improve the photocatalytic activity of g-C₃N₄.In this dissertation,valuable explorations on the enhancement of the photocatalytic organic pollutants degradation activity of g-C₃N₄ were carried out,the two aspects including loading energy band matched photocatalysts and structural adjustment were studied.The following results are mainly obtained:Firstly,the preparation and photocatalytic properties of g-C₃N₄ semiconductor were investigated.The two dimensional semiconductor of g-C₃N₄ with high N4-based photocatalysts.composition,structure,morphology and large surface area was prepared by pyrolysis method.We have discussed the influence of raw materials,reaction time and temperature on the morphology,size and surface area of final products.In addition,we also carefully studied its inner optical properties,which make a good preparation of g-C₃N₄-based compound semiconductor materials for high activity and high stability.Secondly,the enhanced visible-light photocatalytic organic pollutants degradation of g-C₃N₄ was achieved through in-situ growth.Using g-C₃N₄ as precursor,which were synthesized by melamine pyrolysis,g-C₃N₄/Bi2MoO6 and the ternary composites of g-C₃N₄/Ag2WO4/Ag were prepared.It was found that g-C₃N₄-based compounds with suitable band gap have a good visible light absorption performance and can efficiently enhance the separation of photo-generated electrons and holes.Therefore,the g-C₃N₄-based photocatalysts can improve the degradation of organic pollutants and promote the photocatalytic activity under visible light irradiation.Furthermore,we also made in-depth discussions of the mechanism for the as-prepared composite photocatalyst,which can lay the theoretical foundation for preparation of selective g-C3Lastly,porous g-C₃N₄?Pg-C₃N₄?with large surface area was chose as precursor,Pg-C₃N₄/Ag3PO4 and Pg-C₃N₄/BiOBr composite photocatalysts were synthesized by simple mixing or hydrothermal methods.The experimental results showed that the binary coupled photocatalyst could significantly increase the organic pollutants degradation activity under visible light irradiation.The pore structure of Pg-C₃N₄ can enhance the absorption of visible light with a large surface area.Furthermore,close interface contact between Pg-C₃N₄ and other catalysts is also conducive to the transmission of photogenerated carriers and separation of electrons and holes.Therefore,Pg-C₃N₄-based photocatalyst can effectively improve the photocatalytic activity,and has wide application prospect.