Study On Process And Properties Of Preparation Of Porous Carbon And Composite Carbon Nanofibers Prepared Based On Blackwolfberrytwigs

With rapidly decreasing fossil fuels and the increasing demand for energy,it is extremely urgent to develop and utilize renewable energy sources and study new energy storage devices.Supercapacitor is a new type of electrochemical energy storage device that stores energy through an interface double layer formed between the electrode and electrolyte.It has many advantages,such as short charging time,reliable cycle stability,good temperature characteristics,energy saving and environmental protection.The core of the supercapacitor design is to find suitable electrode materials that suitable for different electrolytes.At present,the electrode materials used in capacitors are mainly carbon-based materials,metal compound materials,conductive polymer materials,etc.The resources of these materials are generally some non-renewable materials,such as:coal,petroleum and its derivatives,etc.,which do not meet the national sustainable development perspective.Biomass materials,especially some biomass wastes,can be used as excellent resources for preparing electrode materials due to their low cost,reproducibility,easy availability,and environmental friendliness.In this paper,black wolfberry twigs are used as the basic raw materials,and then it was carbonized and activated by different methods to prepare several supercapacitor electrode materials with excellent performance.At the same time,the prepared materials were systematically characterized and electrochemically tested for their structure and morphology.The main results achieved are as follows:?1?Under the same experimental conditions,activated carbon was prepared by chemical activation method using black wolfberry twigs as raw materials and KOH,NaOH,Na₂CO₃ as activators respectively.The influence of the basicity of the activator on the specific surface area and capacitance of the prepared materials was investigated,and KOH was selected as the best activator for black wolfberry branches.Then KOH was used as the activator for optimization experiments.By comparing the electrochemical performance of the prepared materials under different conditions and parameters,the optimal process parameters were selected:the carbonized product ratio of KOH to black wolfberry branches was 3:1,and the activation temperature was900�C.Under the optimal process parameters,the prepared carbon material has a specific surface area as high as 2046.07 m² g^-1.When the current density is 1 A g^-1,the specific capacitance can reach 355.7 F g^-1.In addition,at a current density of 2 A g^-1,after 5000 charge/discharge cycles,the specific capacitance retention rate can reach 93.6%.?2?Using self-made biomass carbon and polyacrylonitrile as carbon sources,doped with?-cyclodextrin,nanofiber cloth was prepared by electrospinning technology,and cyclodextrin was hydrolyzed with moderate temperature?-amylase,Carbonization was then performed at 800�C for 2 h to obtain porous carbon nanofibers.Under the optimal doping amount of rhenium-cyclodextrin,the specific capacitance of the prepared porous carbon nanofiber material is 215.8 F g^-1(1 A g^-1).When the current density is increased from 1 A g^-11 to 10 A g^-1,the capacitance retention rate is about 78.31%.In order to further improve the power density of the electrode material,on the basis of the optimal enzyme pore expansion,the influence of the amount of zinc acetate added on the capacitance performance of the prepared material was explored.The results show that after a small amount of zinc acetate is added,the specific surface area of the material is increased to 340.75 m² g^-1,and the microporous,mesoporous and macroporous pore structures are simultaneously present.Capacitance performance is also improved to 262.2 F g^-1.After 5000 charge and discharge cycles at a current density of 2 A g^-1,the capacitance retention rate is95.19%,which can be used as an excellent electrode material.?3?The Fe₂O₃/CNFs composite electrode material was prepared by using a simple electrospinning method using self-made biomass carbon and polyacrylonitrile as the carbon source and iron acetylacetonate as the iron source.The effects of the amount of ferric acetylacetonate and the activation temperature on the properties of the materials were explored.The results show that under the best experimental conditions,the prepared Fe₂O₃/CNFs composite electrode material shows excellent capacitance performance in a three-electrode system.When the current density is 1 A g^-1,the specific capacitance can reach 653.8 F g^-1.When the current density is increased from 1 A g^-11 to 10 A g^-1,the capacitance retention rate is 73.57%.After 1000constant-current charge-discharge tests at a current density of 2 A g^-1,the capacitance retention rate was 87.3%.The Fe₂O₃/CNFs composite material is assembled into a button-type symmetrical supercapacitor.The results show that in the aqueous electrolyte,the voltage window can reach 1.2V.