Synthesis Of Hierarchically Porous N-doped Carbon And Application As Supercapacitor Electrode

Supercapacitor is a kind of environment friendlly and clean storage device,which is used in portable electronic equipment,electric vehicle,fuel cell,railway,communication,national defense and other fields.There are still some deficiencies about capacitor electrode materials in some areas,so that developing electrode materials with high voltage window,high energy density and good cycle stability becomes a hot topic in today's world.Based on the energy storage mechanism of double layer capacitance and the previous research,the synthesis of porous carbon material and super capacitor had been studied by us.The main conclusions are as follows:Firstly,hierarchically porous N-doped carbon(HPDC)materials were fabricated in one-step manner via the coupled reactions between unconventional carbon source-polyvinyl dichloride(PVDC)and ZnO.The multiple roles of ZnO could simultaneously guarantee the dehalogenation of PVDC and act as template.A type of hierarchically porous N-doped carbon materials was obtained with a high SSA(1540.2 m2·g-1),abundant porosity and good electrical conductivity.At high temperature,H2O evaporation can produce macroporous structure,and ZnO activation could make a lot of mesoporous and microporous.The effects of calcination temperature,ZnO content,melamine(N source)content and oxide species on the morphology,structure and electrochemical properties of the composites were discussed in detail.The capacitance of the optimized material could achieve 315 F·g-1 in 6.0 M KOH electrolyte(a current density of 0.5 A ·g-1).Aqueous supercapacitors are among the most popular ways of storing energy,many merits considering their low cost,environmental friendly,and safe features.However,relatively low open circuit voltages(OCV)strongly limits their specific energy(S.E.),which is due to water splitting at 1.23 V.Herein,the hierarchically porous N-doped carbon materials(HPDC)fabricated via the dehalogenation of polymer(polyvinyl dichloride,PVDC)were applied as electrodes for symmetric aqueous supercapacitors.Remarkably,the as-made aqueous supercapacitor could achieve a safe OCV of 1.8 V in 1.0 M Li2SO4,thanks to the inactive catalytic performance for water splitting,leading to a high S.E.Of 21.5Wh·Kg-1.We ascribed the enhancement of supercapacitor performance to both the applicable neutral electrolyte and the largely hindered water-splitting activity on HPDC.Our work provided not only reasonably good electrode materials with a facile and low-cost route,but also insightful opinion for further expanding safe working voltage window for higher S.E.aqueous supercapacitors;that is,through suppressing undesirable side reactions of water splitting.Our works is significance for the development of supercapacitors.