Fabrication Of Nitrogen-Doped Graphene And Its Catalytic Application In Organic Reaction

Graphene is a novel two-dimensional honeycomb carbon nanomaterial which has several unique advantages such as strong electron-transporting ability,large surface area,high chemical and mechanical stability.Therefore,graphene has been applied in the field of heterogeneous catalysis.Modification by nitrogen atoms can increase the surface active sites,improve electron transport capability and enlarge surface area,which helps enhance the catalytic activity.Thus the application of well-prepared nitrogen doped graphene(NG)with high catalytic quality to the field of heterogeneous catalysis is of high research significance.In this paper NG was applied as the heterogeneous catalyst to catalyze the reduction reaction of nitrobenzene derivatives and oxidation of benzaldehyde derivatives.In this paper graphene oxide(GO)was prepared by improved Hummers method.Furthermore,four kinds of nitrogen-doped graphene was prepared by hydrothermal and hydrothermal-thermal method.The morphologies and layers of GO and NG were detected by transmission electron microscopy(TEM),high resolution transmission electron microscopy(HRTEM)and scanning electron microscopy(SEM).The X-ray diffraction(XRD)and Raman spectroscopy(Raman)were used to study the microstructure of GO and NG.X-ray photoelectron spectroscopy(XPS)was applied to analyze concrete bonding form and ratio of hetero atoms in the graphene lattice.the content of four kinds of nitrogen in NG were 8.83%,8.03%,6.94% and 3.60%,respectively,and the content of pyridinic nitrogen,pyrrolic nitrogen,graphitic nitrogen and pyridinic-oxygen nitrogen were determined.NG was further prepared as the catalyst for the reduction reaction of nitrobenzene in the research.Experimental results showed that NG could realize efficient and green catalytic reduction of nitrobenzene.The expansion of reactants under the catalysis by NG was successful with no traditional dehalogenation observed.On this basis,this paper further investigated the impact on reactions catalyzed by different types of nitrogen doping.The results of experiments combined with density functional theory(DFT)calculations which demonstrated that the graphitic N had the most preferable catalytic effect.The reaction intermediate state was analyzed by gas chromatography-mass spectrometry(GC-MS)to speculate the reaction mechanism.In addition,NG was proved to having high recyclability.Experimental results demonstrated that NG could also be applied to the catalytic oxidation of benzaldehyde with high catalytic activity.According to the exploration of different catalysts,nitrogen element in NG and the graphene nanosheet structure were two indispensable factors.On this basis,the paper optimized a series of experimental conditions.By using the optimal reaction conditions this paper further explored the reaction conditions of several benzaldehyde with different functional groups.It was found that the above-mentioned substrates could be efficiently catalyzed by NG.What's more,NG also had a strong recyclability for benzaldehyde oxidation.The research extends the field of application for NG regarding the catalytic oxidation and reduction reactions,which proves that there are great prospects and wide expandable applications for NG in heterogeneous catalytic reactions.