| In order to solve the problem of energy shortage and other environmental demand,supercapacitor appears in everyone's field of vision as an efficient new electrochemical energy storage equipment.It has the advantages of rapid charge and discharge of capacitor and the energy storage characteristics of battery.However,electrode material is the key factor affecting the performance and cost of supercapacitor.Due to its unique crystal structure,good electrical,mechanical properties and large specific surface area,carbon material is the first material used in electric double-layer capacitor.Metal-based compound materials have an advantage in specific capacitance,Therefore,this paper investigates the application of carbon quantum dots,carbon nanotubes and cobalt-aluminum bimetallic hydroxide composites in electrochemistry based on the preparation and modification of carbon quantum dots and functionalization of carbon nanotubes.The main studies are as follows:(1)Firstly,three different methods were used to prepare carbon quantum dots.Citric acid was used as carbon source,urea,hydrazine hydrate and ethylenediamine were used as nitrogen source,and nitrogen doped carbon quantum dots were prepared by hydrothermal method.Using glycerol as carbon source and trisodium phosphate as phosphorus source,phosphorus doped carbon quantum dots were prepared by microwave method.Then the carbon quantum dots are prepared by carbonization of green organic matter such as orange peel.The results showed that the carbon quantum dots containing nitrogen will emit yellow fluorescence and the carbon quantum dots containing phosphorus will emit blue fluorescence.There was a large amount of OH-on the surface of carbon quantum dots prepared by hydrothermal method,which had better water solubility and fluorescence.(2)The carbon nanotubes were acidified and oxidized to solve the problem of agglomeration and winding.The carbon quantum dots prepared by hydrothermal method and functionalized carbon nanotubes were added to cobalt aluminum bimetallic hydroxide respectively.The CQDs/CoAl-LDH and FMWCNTs/CoAl-LDH binary composites were synthesized to make the structure more stable.The conductivity,ion dispersion,specific capacitance,structure and electrochemical cycle stability have been improved,showing better electrochemical characteristics.FMWCNTs/CoAl-LDH binary composites have higher specific capacitance and cycle stability.When the current density is 1 A g-1,the specific capacitance of CQDs/CoAl-LDH and FMWCNTs/CoAl-LDH binary composites is 274F g-1,425 F g-1,which is 31.7%and 104.3%higher than that of single cobalt aluminum hydroxide(208 F g-1),respectively.(3)Based on the binary composites,CQDs/FMWCNTs/CoAl-LDH ternary composites were further synthesized,and CQDs/FMWCNTs binary composite carbon materials were obtained in the preparation process,and the ternary materials once again obtained great improvement in electrical conductivity,structural stability,electrochemical reversibility,ion dispersion rate,specific capacitance,and charge/discharge cycle stability compared with single materials and binary composites.The ternary materials have obtained a great improvement in conductivity,structural stability,electrochemical reversibility,ion dispersion rate,specific capacitance and charge/discharge cycle stability compared with single materials and binary composites.Compared with CQDs/CoAl-LDH,FMWCNTs/CoAl-LDH and CQDs/FMWCNTs,the specific capacitance of CQDs/FMWCNTs/CoAl-LDH ternary composites increased by 108.8%,34.6%and 149.8%,respectively.The specific capacitance decreased from 572 F g-1 to 501 F g-1 at different current densities with a capacitance retention of 87.6%.Figure[38]Table[3]Reference[110]... |
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