Research On Electrochemical Performance Of Functional Porous Carbonbased Electrode Materials Prepared From Organic Potassium Salt

With the aggravation of the energy crisis and environmental problems increasingly,it is urgent to develop and use of green and high performance storage devices.Owing to high energy density,superior power density,long service life,and environmental benignity,supercapacitors,a new energy storage device,were chosen as an ideal energy storage system.Therefore,it is of great theoretical significance and application value to develop supercapacitors.Electrode materials are the key factor to determine the electrical properties of supercapacitors.Porous carbon and its composite materials,because of their stable physical and chemical properties,well capacitance retention,pollution-free and other characteristics,were widely used as supercapacitors electrode materials.However,the simple and controllable preparation of high-performance porous carbonbased electrode materials is remains a major challenge.This paper focused on how to improve the performance of supercapacitors electrode materials,we chosed a kind of nitrogen-rich organic potassium salt as carbonaceous precursor prepared nitrogen-doped hierarchically porous carbon materials through self activation.Simultaneously,other synthesis methods,like template-limited method,microwave method and hydrothermal method,were combined for the improvement of pore structure and surface composition.The morphological characteristics,porous structure,surface composition,and crystallinity of the asprepared materials were characterized by a series of technical methods,furthermore,their electrochemical properties were tested by cyclic voltammetry,galvanostatic charge discharge and AC impedance when used as the electrode materials for supercapacitors,for the purpose of selection and construction of porous carbon based electrode materials system for high performance supercapacitors.The main research work are as follows :?1?The in-situ oxygen and nitrogen co-doped hierarchically porous carbons EPCs-T with high specific surface area were obtained from ethylenediaminetetraacetic acid tripotassium salt dihydrate?EDTA-3K?by one-step calcination via self-activation based its nitrogen/oxygen containing and carboxylate groups.The effect of different calcination temperatures were explored,it is found that the content of nitrogen and oxygen decreased with the increase of calcination temperature,while the pore volume and pore size increased.EPCs-800 exhibited ultrahigh specific surface area of 2787 m² g^-1,as well as the best gravimetric capacitance(182.3 F g^-1 at 1 A g^-1),and after 2000 cycles at the current density of 5 A g^-1,the capacitance retention reached initial 95.2%,indicating that the electrode materials had good charge and discharge stability.?2?Hierarchically porous carbon materials,SEPCs-T were synthesized using EDTA-3K as carbonaceous source,SBA^-15 as hard template via domain-limited carbonization.The effects of calcination temperature on the pore structure,composition and other physical and chemical properties and the electrochemical properties of SEPCs-T were discussed.The results showed that SEPCs-T had clear sponge-like structure,and the pore size of pore size decreased with the increase of calcination temperature,while the pore volume and pore size increased with the calcination temperature,SEPCs-800 exhibited the highest specific surface area of 2578 m² g^-1.Under the same conditions,the oxygen/nitrogen content of SEPCs-T were not significantly different from EPCs-T prepared in the previous chapter.SEPCs-700 revealed the highest gravimetric capacitance of 213.8 F g^-1 at the current density of 1 A g^-1.SEPCs-T contained a large number of meso/macroporous structures,which provided effective ion transport channel,the process of ion transport and storage were accelerated,thereby,the enhanced electrochemical performance were better than EPCs-T.?3?In order to enhance pseudocapacitance,improve electrochemical performance,EPCs-800/NiCo₂O₄ composite electrode materials was prepared using EPCs-800 as supporter by two kinds of different heating methods,namely,constant temperature water bath and microwave radiation,induced NiCo₂O₄ nanosheets grown on the surface of EPCs-800 by the combination of urea homogeneous precipitation method and low temperature oxidation method.Both of the two kinds of methods could be able to make NiCo₂O₄ successfully loaded on the surface of EPCs-800,but their growth orientation were different.The NiCo₂O₄ prepared by traditional water bath heating were parallel to the surface of EPCs-800,while the NiCo₂O₄ prepared by microwave irradiation were perpendicular to the carbon surface,and more uniform and compact.As supercapacitor electrode materials,the specific capacitance values of EPCs-800/NiCo₂O₄^-1 and EPCs-800/NiCo₂O₄-2 were 207.6 and 434.8 F g^-1,respectively.Furthermore,EPCs-800/NiCo₂O₄-2 also showed superior capacitive property and excellent cycle stability,as well as lower resistance.?4?Ternary tricobalt tetraoxide/graphene nanosheets/carbon composites?Co₃O₄/GNS/EPCs?electrode material were controllably prepared using cobalt nitrate as metal source,urea as alkali and nitrogen source,EDTA-3K as carbon/nitrogen source and activating agent,and incorporation of graphene nanosheets,through combination of hydrothermal method,high temperature calcination and oxidation at low temperature,successively.The characterization results showed that the activated graphene nanosheets played the role of structure directing and templating,which combined with EDTA-3K drived porous carbons to form composite carbon nanosheets,meanwhile,Co₃O₄ nanoparticles were highly dispersed to avoid stacking each other.Furthermore,the addition of graphene greatly improved the conductance of the composites.The specific capacitance of Co₃O₄/GNS/EPCs electrode materials was 772.4 F g^-1 at the current density of 1 A g^-1,which was much higher than that of EPCs-T,and also revealed good cycling performance,rate characteristics,along with low impedance.The excellent electrochemical properties may be attributed to the synergistic effect of the activated conductive graphene layer,porous carbon,Co₃O₄ nanoparticles,and nitrogen/oxygen doping.