| In recent years,environmental pollution and energy shortages have always became the research hotspots that scientists all over the world are paying attention to.The pollution of industrial wastewater and gas,as well as the massive development of fossil fuels,has pushed us to find alternatives.The use of sunlight as energy to degrade organic pollutants and photocatalytic H2 evolution and CO2 fixation may be a sustainable green way.The graphite polymeric carbon nitride(PCN)has the advantages of relatively suitable band gap(Eg=2.75eV),outstanding thermal stability and chemical "inertness",simple preparation and no harmful metal elements.There are many preparation methods for PCN,and the catalytic activity varies greatly due to the slight changes in the chemical structure prepared by different methods.Therefore,in recent years,experts and scholars in the fields of chemistry,materials,physics,environment,etc.at home and abroad have mainly focused on PCN Extensive research on different chemical or physical modifications of the surface in order to obtain higher catalytic activity.This study found that the surface structure modification of PCN obtained by different methods has a very complicated correlation with the catalytic performance,and the detailed tracking of chemically active species can well explain the internal mechanism of the catalytic activity change process.The first chapter of this paper mainly introduces the photocatalytic technology and principle,the common synthesis methods and basic structural properties of PCN.Next,introduce the main research work of this paper through two chapters,as follows:(1)Obtain the ultra-thin PCN photocatalyst by oxygen etching,and explore its morphology and physical and chemical properties through various basic characterizations.The results show that the prepared sample Reannealed-450 has an ultra-flaky structure,and its SBET is as high as 165.74 m2g-1,which is more than 9 times that of the original PCN.The efficiency of degrading organic pollutants RhB and MO molecules has been significantly improved.The reduction in the lateral size and thickness of the "bulk" PCN not only provides more active sites for photocatalytic reactions,but also enhances the separation of photo-induced electron-hole pairs,making it easier to migrate to the surface of the material to participate catalytic reaction.(2)By loading Ag-related substances on the sample Reannealed-450 to form a heterojunction,the charge separation efficiency is significantly improved.But the morphology obtained under SEM seems to have re-formed a "bulk" structure.While the SBET is significantly reduced,the different degradation behaviors of the heterojunction to RhB and MO molecules arouse interest.It can be found that the photocatalytic degradation of organic pollutants does not seem to be affected by a single factor,but rather the result of the combined effects of the contribution of active free radicals and efficient charge separation.Furthermore,a suitable photocatalytic degradation model was constructed based on the above assumptions to explain the degradation behavior of the above five photocatalysts.Finally,this article summarizes the related work.Different modifications to the precursor PCN not only change the separation efficiency of charges,but also regulate the contribution of active free radicals,revealing that changes in the microstructure of PCN may cause outstanding changes in photocatalytic activity. |
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