| With the rapid development of the national economy,environmental problems have become increasingly serious,among which water pollution is a major problem.However,water pollution caused by industry is the most serious because of its complex composition,many pollutants,and difficulty in degradation.Traditional sewage treatment methods have high selectivity,high cost,low efficiency and incomplete degradation.Photocatalytic technology is a technology that can convert solar energy into chemical energy.It has attracted widespread attention because of its high efficiency,energy saving,environmental protection,low cost,and thorough degradation.Ti O2 is the earliest and most commonly used semiconductor material as a photocatalyst,but Ti O2 has a wide band gap（3.2 e V）and can only absorb and utilize ultraviolet light,resulting in low utilization of sunlight.Therefore,it is urgent to find new semiconductor photocatalytic materials.Graphite-like carbon nitride（g-C3N4）is a metal-free organic semiconductor material with a narrow band gap（2.7 e V）,can absorb and utilize visible light,is non-toxic and environmentally friendly,and has stable chemical properties.However,its small specific surface area and fast photo-generated electron-hole pair recombination rate results in poor photocatalytic activity.Therefore,this article modified the two problems of g-C3N4.This article is divided into five chapters:Chapter 1:The introduction mainly introduces photocatalytic technology,semiconductor materials（including inorganic semiconductors and organic semiconductors）,and carbon nitride.Chapter 2:This chapter mainly explores the problem of the small specific surface area of g-C3N4.The method of high temperature thermal polymerization is adopted to change the specific surface area by controlling the calcination temperature to explore the effect of calcination temperature on the specific surface area of g-C3N4.Then by applying the prepared g-C3N4 to visible light to degrade methyl orange,the photocatalytic activity of the catalyst was evaluated.XRD,FT-IR,SEM,TEM,BET,UV-vis DRS and XPS were used to characterize the phase and structure of the catalyst.The results show that the g-C3N4 prepared by this method has a double pore structure,and as the calcination temperature increases,the specific surface area gradually increases（all above 100 m2/g）,the visible light absorption increases,the band gap decreases,and the photocatalytic activity.Chapter 3:This chapter aims at the fast recombination rate of photogenerated electron-hole pairs of g-C3N4,and suppresses the recombination of photogenerated electron-hole pairs by constructing a heterojunction.g-C3N4 is prepared by the thermal polymerization method in Chapter 2,and the calcination temperature is 570℃from an economic point of view.Ag Br nanoparticles are deposited on the surface of g-C3N4 by the deposition-precipitation method to construct a heterojunction.The prepared catalyst was applied to the visible light catalytic degradation of methyl orange,and the phase and structure of the catalyst were studied by XRD,SEM,TEM,BET,UV-vis DRS,PL and XPS.The results show that the loading of Ag Br does not change the dual-porous structure of g-C3N4.Compared with pure g-C3N4,the composite photocatalyst has significantly enhanced absorption in the visible light region,reduced band gap,and recombination rate of photogenerated electron-hole pairs.It has also been significantly inhibited,thereby enhancing its photocatalytic activity.Chapter 4:This chapter still uses the thermal polymerization method of Chapter 2 to prepare g-C3N4,using FeSO4 as the iron source,and calcining at high temperature to obtain a composite photocatalyst of Fe2O3/g-C3N4.The composite photocatalyst was applied to the visible light degradation of methyl orange,and the phase and structure of the catalyst were studied by XRD,BET,UV-vis DRS,PL and XPS.The results show that compared with pure g-C3N4,the composite photocatalyst has significantly enhanced absorption in the visible light region,the photo-generated electron-hole pair recombination rate is also significantly suppressed,and the photocatalytic activity is relatively enhanced.Chapter 5:Summarize the work done in this article,and put forward suggestions based on the research results of this article on future research directions for g-C3N4. |
