Preparation Of Nitrogen And Sulfur Co-doped Graphene Gels And The Application In Supercapacitors

As a new type of energy storage devices,the supercapacitor has some advantages of fast charge/discharge rate,high power density,long cycle life,and good safety performance,and thus it has a very wide application prospects in energy sources,transportation,military,biotechnology,and so on,and has attracted worldwide attention.Compared with the widely used lithium-sulfur batteries and lead-acid batteries,the supercapacitor has the higher power density and better cycle stability,but lower energy density limits its application in many fields.The electrode materials are the most important component of supercapacitors.The properties of the electrode materials determine the performance of the supercapacitor,thus a large number of researches have focused on electrode materials.The electrode materials of supercapacitors include carbon materials,transition metal oxides,conductive polymers,and so on.Carbon materials were firstly used as electrode materials for supercapacitors and were used widely.Graphene(GR)is considered to be the ideal electrode material for supercapacitors because of its high specific surface area,good electrical conductivity,thermal stability,chemical stability,and wide voltage windows.Graphene aerogel(GA)is a kind of three-dimensional graphene materials,which consists of self-assemble two-dimensional graphene by hydrogen bonds,functional groups,and conjugate ? bonds.The GH can effectively inhibit the agglomeration of graphene,so its application is very extensive.In this paper,some heteroatoms co-doped graphene aerogels were prepared and used as electrode materials in supercapacitors.The major contents are as follows:1.N and S co-doped graphene aerogel materials(N/S-GH1)were prepared with graphene oxide(GO)and reductive ionic liquids as the raw materials by controlling the composition,reaction temperature,and time.The N/S-GH1 as electrode materials assembled into the double-layer supercapacitors,and their electrochemical performances were tested by a variety of electrochemical methods.The results showed that specific capacitances are 182 F/g and 127 F/g with the current densities of 1 A/g and 10 A/g,respectively,with the 99.9 Wh/kg and 62.3 Wh/kg energy density.2.A series of N and S co-doped graphene aerogels were synthesized through the reaction of GO and2-mercapto-1-methylimidazole as nitrogen/sulfur sources and reducing agent at different reaction time,temperature,and material proportion.When the N/S-GA2 prepared under optimum condition was used as the electrode material for supercapacitors.Their specific capacitance,energy density,and power density reached 212 F/g,116.9 Wh/kg,and 1.0 kW/kg with the current density of 1 A/g.The specific capacitance,energy density,and power density are 162 F/g,82.1 Wh/kg and 9.5 kW/kg under the current density of 10A/g.Compared with the N/S-GA1,N/S-GA2 exhibited higher capacitance performance.3.Non-toxic 2-mercaptobenzimidazole reacted with GO by one step hydrothermal method to obtain N and S co-doped graphene aerogel materials(N/S-GA3)at 200°C and at 2:1(the mass ratio of2-mercaptobenzimidazole to GO).Under current density of 1 A/g,the specific capacity of as-constructed supercapacitors was 206 F/g,the corresponding energy density and power density were 104.7 Wh/kg and1.0 kW/kg,respectively.Since the raw materials used in this method are non-toxic and harmless,this method has great application value in the preparation of supercapacitors.In this paper,N/S co-doped graphene aerogels were prepared with three different reducing agents.All of them exhibited higher specific capacitiance and energy density,and have great application prospects.