Preparation Of G-C₃N₄ Nanosheets And Their Supported And Application On Cellulose Aerogels

Graphite phase carbon nitride（g-C₃N₄）is a non-metallic polymer photocatalytic semiconductor with a layered structure similar to graphite,which has the advantages of easy availability,high stability,and no secondary pollution.The band gap（2.70 eV）can make the photocatalyst visible light has a certain absorption and is an important new type of visible light-responsive photocatalyst,which plays a significant role in tackling energy and environmental problems.At present,the preparation of g-C₃N₄ chiefly adopts the thermally induced self-polymerization strategy.This method has cheap raw materials,simple operation,and industrial production,but it also faces many problems,such as the serious interlayer accumulation of the obtained bulk g-C₃N₄ structure,resulting in its small specific surface area,coupled with its own photo-generated carriers easy to recombine and the utilization of visible light in solar energy is still not high.This work uses the mechanical milling method to exfoliate the g-C₃N₄ photocatalyst to improve its photocatalytic activity.In addition,in view of the problem that g-C₃N₄ is difficult to recycle as a powder photocatalyst.In this work,g-C₃N₄ is loaded in a cellulose-based aerogel porous material,which can realize recycling without affecting its photocatalytic activity,and has a considerable application prospect in practical applications.Exfoliation of g-C₃N₄:Adopts thermal induced self-polymerization with urea,thiourea and melamine as the three precursors for bulk g-C₃N₄,respectively,it is revealed that the specific surface area(95.35 m²·g^-1)of g-C₃N₄ prepared from urea is 3.5 times and 5.5 times that of thiourea and melamine,respectively.The degradation experiments showed that g-C₃N₄ prepared with urea as the precursor had the highest photocatalytic activity.On this basis,the influence of the heating rate on the photocatalytic activity was explored,and the study showed that the slower the heating rate was,the better the photocatalytic performance was improved.The bulk g-C₃N₄ prepared with urea as the precursor was subjected to wet ball milling to obtain g-C₃N₄ nanosheets（WBCN）.The results showed that the ball milling speed has an important impact on the structure and performance of the g-C₃N₄ nanosheets.The higher the milling rate,the smaller the size and the number of layers of WBCN obtained,the better the dispersibility,and the better the photocatalytic property.However,when the velocity is increased to 300 rpm,the excessive reduction in size leads to the destruction of the conjugate structure,which is not conducive to the photocatalytic performance.Therefore,when the rotation speed is 150 rpm in the experiment,the prepared g-C₃N₄ nanosheets show the best photodegradation of Rhodamine B（RhB）.Loading of g-C₃N₄ nanosheets:The WBCN nanosheets prepared by exfoliation were co-assembled with cellulose and its derivatives to prepare g-C₃N₄ nanosheets@cellulose aerogel（WBCN@CA）composite material,which solved the problem of photocatalyst recycling use of difficult problem.At the same time,it is found through mechanical performance test that the prepared aerogel has good compression recovery,which provides strong support for recycling.When the load of photocatalyst is 30%is the best proportion.Too little amount will affect the photocatalytic efficiency,and too much amount will cause the agglomeration of nanosheets,which is detrimental to photocatalytic activity.To verify its actual photodegradation,the composite material was exploited to degrade the target pollutants（Rhodamine B,methyl orange,methylene blue）in the lake water.It was found that the photodegradation time would be prolonged due to the influence of the lake water quality,but in the end,pollutants can still be removed very well,which fully proves its practical applicability.