Synthesis And Photocatalytic Properties Of Mesoporous Graphite Carbon Nitride

Energy and environment issues must be faced in the evolution of human civilization.With the progress of science and the rapid development of economy,various problems are exposed.On the one hand,coal,oil and other non-renewable fossil energy are consumed in large quantities,and the current reserves are not enough to support the sustainable development of mankind.On the other hand,carbon dioxide and other gases produced by fossil energy combustion are discharged into the air,and wastewater and waste residue produced in industrial production are directly discharged into the environment,causing serious environmental problems.Therefore,the search for reliable clean energy and effective treatment of pollutants has become a major problem to be solved urgently.Photocatalysis is an important means to effectively utilize sunlight,which shows great potential application value in the field of energy production and environmental cleanliness.At present,the catalysts are mainly semiconductors.Graphite carbon nitride,as a semiconductor with stable structure,adjustable band gap,low toxicity and low cost,has attracted wide interest.However,the low specific surface area and easy recombination of photogenerated carriers also restrict the photocatalytic efficiency.In view of the above problems,the main research contents of this dissertation are divided into three aspects: Firstly,graphite carbon nitride was synthesized successfully by a thermal condensation method,and a series of carbon nitride samples with different photocatalytic properties were obtained by adjusting the preparation temperature.The obtained carbon nitride in graphite phase was systematically characterized,and the relationship between the photocatalytic activity and the preparation temperature was revealed by taking photodegradation of Rhodamine B(RhB)as an example,which laid a foundation for further research on mesoporous carbon nitride.Secondly,a series of mesoporous graphite phase carbon nitrides with large specific surface area were successfully synthesized by introducing ammonium sulfate as bubble template,and the specific surface area was increased by nearly 19 times.Taking photodegradation of RhB and P-nitrophenol(PNP)as examples,the relationship between the photocatalytic performance and the material morphology was revealed.The mesoporous graphite phase carbon nitride presented better photocatalytic performance,which is mainly due to the following reasons: first,the mesoporous structure provides a larger specific surface area,which gives it a stronger light absorption capacity;secondly,the porous structure of mesoporous graphite phase carbon nitride enables multiple scattering of light inside the material,further enhancing the light absorption capacity;thirdly,porous structure can improve the carrier separation rate,make more electrons transfer to the catalyst surface,and lay the foundation for the next reaction.Finally,sulfur-doped mesoporous graphite phase carbon nitride was prepared by thermal polycondensation and then characterized systematically.The experimental results showed that the photodegradation efficiencies of RhB solution by sulfur-doped mesoporous graphite carbon nitride with different doping ratios are higher than those of the pure graphite carbon nitride dioxide under simulated solar irradiation,which increased from 54% to 74% after five minutes.The synthesis method reported in this dissertation can be extended to synthesize mesoporous graphite-phase carbon nitride materials by using different templates,showing great application potential in the fields of environmental purification(photodegradation)and solar energy conversion(photolysis of water,reduction of carbon dioxide,etc.).