Synthesis And Electrochemical Energy Storage Properties Of Hierarchically Porous Doped Carbon Based Electrode Materials

Owing to the unique structural and compositional properties of doped carbon materials with hierarchically porous structure play a vital role in high energy storage performances when used as electrode materials for supercapacitors.As reported,the micropores in hierarchically porous carbon materials provide locations for adsorption and accommodation of electric charges,the mesopores work as the immigration channels for the rapid transport of electrolyte ions,while the masopores serve as the ion-buffering containers,which facilitate the enhancement of the electrochemical double layer capacitances.In addition,doping heteroatoms could enhance the redox activity of the carbon based electrode materials,and thus to elevate the psedocapacitances availably.However,until now,most reported methods for the synthesis of hierarchically porous doped carbon materials contains several steps,and it is inadequate to modulate their composition and structure through these methods.Therefore,it is very meaningful for us to develop facile methods to prepare hierarchically porous carbon materials with controllable structure and composition.In order to prepare hierarchically porous carbon materials with controllable structure and composition,we try different methods,including:ionic-liquid-templating method,hydrothermal treatment and composing process.The main points are as follows:1.By using ionic liquid?IL?as pore template and heteroatoms source,we prepared the layered boron-and-nitrogen-doped carbon material with hierarchically porous structure through the co-calcination process of urea,IL and glucose.By tuning the added amount of IL and the calcination temperature,the hierarchically porous structure,conductivity and doping contents of the obtained products could be well controlled.The hierarchically porous boron-doped graphitic carbon nitride nanosheet electrode material exhibits high electrochemical energy storage performances,including high specific capacitances of 620.0 F g^-1 at 0.1 A g^-1,a high energy density of 86.1 Wh kg^-1 and a stable cycling durability with no capacitance declination after 2500 charge-discharge cycles.This method provides a new way for preparing boron-and-nitrogen-doped carbon material used as electrode material for supercapacitors.2.Mesoporous graphitic carbon nitride was firstly obtained by the co-calcination of urea and IL.Then,the obtained precursor was coated with glucose-based-carbon through a hydrothermal process and finally calcined at a higher temperature in pipe furnace to acquire the final foam-like porous boron-and-nitrogen-doped carbon material.The electrode material with hierarchically abundant pores and high doping contents?28.13 at%?.Similarly,by tuning the added amount of IL during the first step,the parameter of hydrothermal treatment,the porous structure and the composition of the final product could be well controlled.This prepared material exhibits high energy storageperformance,including a large specific capacitance of 660.6 F g^-1 at 0.1 A g^-1and a high capacitance retention after 10,000 cycles.3.By co-calcination of ZIF-derived nitrogen-doped carbon nanoparticles with urea and glucose,the ZIF-8-derived nitrogen doped carbon nanoparticles/graphitic carbon nitride composite material could be obtained.The introduction of nitrogen-doped carbon nanoparticles effectively changed the closely-stacked structure of graphic carbon nitride layers.The obtained product also exhibits a hierarchically porous structure with high doping contents,which endows it with high electrochemical energy storage performances,including high specific capacitances of 495 F g^-1 at 0.1 A g^-11 in three-electrode system.When assembled as electrode materials in symmetrical two-electrode system,the as-prepared composite electrode material could exhibit a high energy density of 11.89 Wh kg^-1.This method provides a new idea and direction for the preparation of hierarchically porous carbon materials.