Dielectric Barrier Discharge Modification And Electrochemical Properties Of Graphene Oxide-based Materials

With the continuous development of energy technology,modification of graphene-based materials with excellent physical and chemical properties have attracted wide attention to obtain energy storage devices with excellent performance.In this thesis,graphite oxide（GO）was treated with dielectric barrier discharge plasma.By changing nitrogen source（NH₃,pyrrole）and plasma parameters,nitrogen-doped graphene-based materials were prepared for supercapacitor electrode,and their structure and electrochemical performance were analyzed.The main research results are as follows.1.The influence of NH₃/Ar volume ratio and discharge time in NH₃/Ar dielectric barrier discharge plasma on the structural and electrochemical properties of GO-P were investigated.X-ray diffraction（XRD）analysis showed that the diffraction peaks of GO-P of the NH₃/Ar plasma-treated samples at 2θ=11.02°decreased and the diffraction peak shifted to a higher angles compared to GO.This is due to the decrease of lattice constant caused by N-doping and the increase of disorder caused by the increase of defects.The sample prepared at NH₃:Ar=1:3 with a discharge time of 40 min had the best electrochemical activity with the highest specific capacitance(187.7 F·g^-1)at a current density of 1 A·g^-1and a cycling efficiency of80%after 1000 cycles at a current density of 3 A·g^-1.This can be attributed to its high N-doping content（7.6 at.%）,N/C atomic ratio（0.10）,graphitic nitrogen content（42.4%）and I_D/I_Gratio（1.08）.The results of the diagnostic study of the discharge mechanism showed that the decrease of the discharge breakdown voltage at NH₃:Ar=1:3 produced a high number of current pulses and high current pulse amplitude and generated more NH radicals.2.Using pyrrole as the nitrogen precursor,the influence of pyrrole monomer addition on the electrochemical performance of PPy/GO-P prepared by H₂/Ar dielectric barrier discharge plasma was investigated.When the volume ratio of pyrrole to GO solution was 5:50（1:10）,the sample showed better electrochemical performance.Based on this,the effects of discharge voltage and discharge time of H₂/Ar plasma on the structural and electrochemical properties of PPy/GO-P were further investigated.When the discharge voltage was 19 k V and the discharge time was 40 min,the sample had the best electrochemical properties and the same highest specific capacitance(226.06 F·g^-1)at a current density of 1 A·g^-1.It has 80.3%cycling efficiency after 1000 cycles at 3 A·g^-1current density.Structural analysis showd it has the highest N-doping content（7.47 at.%）and N/C atomic ratio（0.090）,with graphitic nitrogen content of 15.9%and the largest I_D/I_Gratio（1.08）among the N-doped types,which was attributed to the synergistic effect of polypyrrole and N-doping contributing to the higher pseudocapacitance,promoting redox reactions and improving carrier mobility.In this thesis,N-doped graphene-based materials with good performance were prepared by atmospheric pressure dielectric barrier discharge plasma technique,which has the advantages of fast,green and easy operation.This provides a new idea for the modification of graphene-based materials.