Preparation And Electrochemical Properties Of ZnO Nanoparticles Supported On N-doped Hierarchically Porous Carbon

ZnO is considered as a promising electrode for supercapacitor due to its earth abundance,non-toxicity,low raw material cost for synthesis,and good electrochemical activity.However,its low conductively and poor cycling stability during fast discharge/charge process hinder their wide applications.Loading ZnO nanoparticles on hierarchically porous carbon support is one of effective ways to response above issues due to the prominent advantages of hierarchically porous carbon including large surface areas,superior electric conductive,and mechanical and chemical stability.In addition,studies have shown that doping nitrogen heteroatoms into carbon supports can significantly enhance the electrochemical performance of electrodes.In this work,two types of nitrogen-doped hierarchically porous carbon,including nitrogen-doped macro-/mesoporous carbon and nitrogen-doped mesoporous carbon sphere,supporting ZnO nanoparticles.And their electrochemical properties were studied.Specific researches as follows:（1）Three dimensional ordered nitrogen-doped macro-/mesoporous carbon material（N-OHPC）were prepared by using ordered SiO₂ submicron array,F127,dicyandiamide and resol.The N-OHPC has a high BET specific surface area(1068.3 m² g^-1).Subsequently,supercapacitor composite electrode materials were prepared by loading ZnO nanoparticles onto N-OHPC by sol-gel method,and their electrochemical properties were studied.The electrochemical performance was optimized based on the content of ZnO in the composite.The as-synthesized ZnO/N-OHPC（40%ZnO）exhibits a maximum specific capacitance of720 F g^-1 at 1 A g^-1 and 475 F g^-1 at 10 A g^-1.It exhibits a great rate ability（66% capacitance retention）and durability（90% of the initial capacitance was obtained after 30,000 cycles）（2）Nitrogen doped mesoporous carbon spheres（N-OMCS）were prepared by using SiO₂ template with inverse opal structure,F127,dicyandiamide and resol.Subsequently,supercapacitor composite electrode materials were prepared by loading ZnO nanoparticles onto N-OMCS by sol-gel method,and their electrochemical properties were studied.The electrochemical performance was optimized based on the content of ZnO in the composite.The as-synthesized ZnO/N-OMCS（40%ZnO）exhibits a maximum specific capacitance of651 F g^-1(917.9 F cm^-3)at 1 A g^-1 and 501 F g^-1(706.4 F cm^-3)at 10 A g^-1.It exhibits a great rate ability（77%capacitance retention）and durability（94.2%of the initial capacitance was obtained after 30,000 cycles）...