Research Of Synthesis And Characterization Of Functional Biomass-derived Carbon Materials For Electrochemical Performance

From the age of steam to the age of electricity,and from the age of electricity to the age of information,the development of human society is always accompanied by the innovation of energy technology.Since the industrial revolution,energy and environmental problems have been restricting the development of all countries.Especially with the miniaturization and mobility of electronic devices,people have put forward higher requirements for energy supply methods.As an advanced electrochemical energy storage device,supercapacitors are favored by researchers in various countries due to the ultra-fast charge and discharge rate,ultra-high power density and ultra-long service life.However,the low energy density restricts their use.Electrode material is the key factor to determine the energy storage performance of supercapacitors.Therefore,this paper aims to optimize the synthesis method of carbon materials to develop practical carbon-based double-layer supercapacitors with high energy density and high power density.The specific contents of the work are as follows:?1?The by-product of degumming industry,sericin,was used as a nitrogen and carbon source.The carbon materials with rich pore structure were prepared via two-step method with KOH as activator.The tests show that the unique hierarchical porous structure gives the carbon material excellent specific capacity and excellent transmission rate.The specific capacity of the prepared AC-1 at the current density of 0.5 A g^-1 is 228.5F g^-1.At the current density of 10 A g^-1,the capacity retention rate after 10,000 cycles is84%of the original capacity.?2?Considering the corrosive problems which may be caused by the use of KOH in Work 1,we introduced a green one-step activation/blowing strategy to intervene the carbonization process of sericin,and eventually we successfully produced carbon nanosheets with porous structure.Surprisingly,the carbon nanosheets also spontaneously formed fluffy broccoli-like clusters during the carbonization process.The customized layered pore structure facilitates the adsorption and transfer of electrolyte ions between two-dimensional carbon layers,and the high level of heteroatomic doping contributes to the additional pseudocapacitance effect.The prepared NPCN-4-700 exhibits the high mass specific capacity of 214.5 F g^-1 at the current density of 0.5 A g^-1.the obtained carbon materials exhibited a typical double-layer behavior with an outstanding specific capacitance of 214.5 F g^-1 at 0.5 A g^-1 in 6 mol L^-1 KOH and high capacitance retention over 87%at 10 A g^-1 after 10000 cycles.?3?Sericin is a natural macromolecule with high nitrogen content,we attempt to modify graphene using biomass nitrogen source.A solution of concentrated sulfuric acid containing sericin was applied to the oxide intercalation of flake graphite.The prepared N-doped oxide graphene had a nitrogen content of 3.7 at%.The N-doped reduced graphene was prepared by hydrothermal reduction with a nitrogen content of about 1.9at%.Further tests showed that the nitrogen atoms in GO were mainly graphitic nitrogen,which was partially converted to pyrrolic nitrogen after hydrothermal reduction.The specific capacity of NrGO prepared at the current density of 0.5 A g^-1 was 227.8 F g^-1.The capacity retention rate after 10,000 cycles at the current density of 10 A g^-1 is 74%of the original capacity.?4?The reduced graphene prepared by hydrothermal reduction in work 3 still has a large number of carbon layers that are not effectively separated.In order to improve the surface utilization of graphene,in this chapter,we introduce a solid-phase assisted microwave method for rapid preparation of 3D graphene in the air.Thanks to the high dielectric loss of acetylene black,the whole microwave stripping process can be completed in tens of seconds.The preparation speed is fast and the stripping effect is good.The prepared 3d graphene shows an increased specific surface area and a wettable internal space.At the current density of 0.5 A g^-1,the high mass specific capacity of 327.1 F g^-1was displayed.At the current density of 5 A g^-1,the capacity retention rate after 20,000cycles is 85%of the original capacity.Excellent electrochemical properties and rapid preparation methods are expected to provide guidance for the preparation of large doses of graphene-like materials.