Preparation And Properties Of Graphitc Carbon Nitride-based Composites

People’s increasingly convenient lifestyles are inseparable from the continuous progress of science,technology and industry,and the damage to the environment should not be ignored while innovating in production.In order to solve the pollution of natural water resources in production and life,scientists use semiconductor photocatalytic technology to degrade organic pollutants in water.Among them,graphitc carbon nitride（g-C₃N₄）,as an excellent conjugated polymer semiconductor material,can not only be applied to photocatalytic degradation,but also can decompose water to hydrogen under the action of solar energy.g-C₃N₄ can be easily prepared by calcining a substance containing nitrogen-rich precursors by a simple thermal polymerization method,and g-C₃N₄ with different morphologies,specific surface areas,and pores can be prepared by different nitrogen-rich precursors and preparation methods.In addition to its catalytic activity under ultraviolet light,g-C₃N₄ also has a certain response to a wide range of visible light.Because pure g-C₃N₄ has the disadvantages of relatively large band gap width and easy recombination of photogenerated electron-hole pairs,it needs to be structurally modified.In this study,melamine was directly used as a precursor,and g-C₃N₄ nanosheets were prepared by thermal polymerization.The non-precious metal material tungsten diselenide（WSe₂）is uniformly supported on the surface of g-C₃N₄ by the hydrothermal method with simple operation method and relatively high safety factor,forming a WSe₂/g-C₃N₄composite material,and the visible light range test of photocatalytic activity for degradation of organic dyes in water.After irradiating for 100 minutes under a simulated light source,the decolorization rate of the WSe₂/g-C₃N₄ composite material for photocatalytic degradation of methyl orange（MO）solution reached 98.7%,while the pure g-C₃N₄ decolorization rate was only 87.6%.In addition,the decolorization rate of RhB dye reached 94.5%,while the decolorization rate of g-C₃N₄ was only 71.7%under the same reaction conditions.Based on the analysis of the chemical structure,micro-morphology,and photoelectric properties of WSe₂/g-C₃N₄ composites,the reaction mechanism of photocatalytic degradation of organic dyes in semiconductor materials was preliminarily studied.The heterojunction formed by the tight binding between WSe₂ and g-C₃N₄ promotes accelerated charge transfer and effectively inhibits photo-generated electron-hole pair recombination.The lamellar WSe₂ can increase the photocatalytic reactive sites and enhance the absorption range of visible light,thereby improving the photocatalytic activity of degrading organic pollutants.