Structural Regulation And Catalytic Properties Of C/g-C₃N₄ Composites

In the past decades,the rapid consumption of fossil fuels and increasing environmental damage have plagued people’s normal life.Therefore,we need to seek good solutions to ease the contradiction between environmental problems and energy crisis.Photocatalysis technology mainly uses clean energy such as solar energy to realize its functions,and has attracted wide attention for its diversified potential in energy and environmental applications.Graphite phase carbon nitride（g-C₃N₄）is considered to be one of the most valuable materials for photocatalytic degradation of pollutants and photocatalytic cracking of water due to its advantages of low cost,simple synthesis and high physicochemical stability.However,the rapid electron hole recombination rate and small specific surface area of the original g-C₃N₄ limit its photocatalytic performance.In this paper,the photocatalytic performance of g-C₃N₄ was improved by regulating the precursor structure,and the relationship between the precursor structure and the structure of subsequent calcined products was studied.Specific work is as follows:（1）glutaraldehyde（GA）containing aldehyde group was introduced into melamine（MA）to form three GA/MA precursors connected by C=N chemical bonds.After calcination,g-C₃N₄ and C complex catalyst was obtained.With the increase of glutaraldehyde,the content of chemical bond increases,and the lamellar structure becomes more and more compact.It can be seen from the thermal decomposition kinetics that the C=N chemical bond will restrict the conversion of melamine to melem,and eventually form a composite catalyst with a closer interaction between g-C₃N₄ and C.Thus,it has better photocatalytic performance than the original g-C₃N₄.（2）Using dicyandiamide and glutaraldehyde as raw materials,three kinds of GA/DCDA precursors with balanced/unbalanced hydrogen bond interaction were obtained by adjusting the amount of glutaraldehyde（GA）.And C-GA/g-C₃N₄composites were obtained after calcination.The obtained C-GA/g-C₃N₄ composite catalyst showed different photocatalytic activity for methylene blue degradation.Compared with the original g-C₃N₄,the photocatalytic activity of C-GA/g-C₃N₄-2 composite was increased by 3.37 times.According to the analysis of thermal decomposition kinetics and structural characterization,the balanced interaction in the structure of GA/DCDA-2 precursor can promote the conversion of dicyandiamide to melamine,and more C-GA would be formed after glutaraldehyde carbonization,which would form a more closely interacting composite catalyst composite catalyst with g-C₃N₄.The close interaction and higher content of C-GA can effectively promote the separation of photogenerated carrier and visible light absorption,so as to improve its photocatalytic performance.（3）Chitosan was selected as carbon source,CS/DCDA precursor with hydrogen bond interaction was prepared through freeze-drying and ordinary drying,and C-CS/g-C₃N₄composite was obtained after calcination.The results show that the freeze-drying process can produce stronger interaction between chitosan and dicyandiamide,which leads to the formation of more complex carbon with stronger interaction and larger specific surface area in C-CS/g-C₃N₄-2.This not only enhances the separation of photoelectron-hole,but also provides a large number of reactive sites for photocatalytic degradation of pollutants.Thus,C-CS/g-C₃N₄-2 has better photocatalytic performance.Figure[44]Table[5]Reference[132]...