The Study On Structural Control Of Carbon Nitride And Its Photocatalytic Performance

As a new organic semiconductor material with visible light response,graphitic phase carbon nitride（g-C₃N₄）has attracted the attention of researchers because of its graphene-like planar two-dimensional lamellar structure,high thermal stability,chemical stability and easy material preparation.However,the inherent defects of g-C₃N₄ itself have severely limited its application in the photocatalytic.In order to improve its performance and thus ensure efficient photocatalytic applications,different method have been used to modify g-C₃N₄ samples.The main focus of this paper is the modification of g-C₃N₄ by modifying the band gap structure as well as forming heterojunction composite catalysts.Based on this,the main research contents are as follows:（1）Porous g-C₃N₄ nanosheets photocatalysts were successfully prepared by a simple one-step calcination method.The g-C₃N₄ was modified by mixing and calcining different amounts of glucose with melamine,and the improvement of the morphology,band gap structure and photocatalytic performance of the as-prepared sample were observed by a series of characterizations.The effect of calcination by mixing glucose with melamine is to change the carbon nitride morphology,the introduction of carbon atoms and defects in the material.During calcination,glucose generates a large amount of gas to split the bulk carbon nitride into porous carbon nitride sheets,which increases the specific surface area of the material.The introduction of defects and carbon atoms into the carbon nitride structure provides more active sites for photocatalytic reactions.The sample with the best photocatalytic degradation performance was calcined glucose with 1%mass ratio（1wt%Glu-CN）,and the photocatalytic degradation efficiency of MO was 5.75 times higher than that of bulk CN.（2）The g-C₃N₄/Bi₁₂O₁₇Br₂ heterojunction composite photocatalysts were obtained by mixing different ratios of porous g-C₃N₄ nanosheets with Bi₁₂O₁₇Br₂ using a simple hydrothermal synthesis method.A series of characterization tools were used to characterize the heterojunction composite catalysts,and to compare the photocatalytic performance of the prepared materials.The sample with the best photocatalytic performance was the sample with 0.3 g of g-C₃N₄ added in the reaction system（BCN-3）.The photocatalytic degradation performance of the BCN-3 sample was 5.4 and 4.0 times higher than pristine g-C₃N₄ and pristine Bi₁₂O₁₇Br₂,respectively.The formation of heterojunction photocatalysts greatly improved the performance of photocatalytic degradation and enhanced the separation and transfer rate of photogenerated carriers.Figure[26]table[5]reference[181]...