Preparation Of Three-dimensional Carbon Composite Materials And Their Application In Electrode Materials For Supercapacitors

Supercapacitors have attracted widespread attention and application in the field of energy storage due to their high-power density,fast charging and discharging speed,long cycle life,wide operating temperature range,low cost,and environmental friendliness.Electrode materials are one of the most critical factors in improving the performance of supercapacitors,and carbon-based materials are widely used electrode materials for supercapacitors.Because of its high specific surface area,excellent conductivity,good electrochemical stability,graphene has become an excellent electrochemical electrode material.Graphdiyne is a two-dimensional planar structure formed by sp and sp²hybridized acetylene bonds and benzene rings.Similar to the structure of graphene materials,it has high conjugation,many active sites,controllable heteroatom doping possibility,good stability,which makes it important in the fields of photoelectricity,energy,catalysis,and other energy storage.Carbon nanotubes are one-dimensional quantum material composed of carbon sp² hybridization.Due to its unique tubular structure and the feasibility of material modification,the electrochemical performance of supercapacitors can be effectively enhanced.However,there are also some issues for the carbon-based materials as used as electrode materials for supercapacitors.Especially because two-dimensional planar carbon materials are prone to agglomeration and stacking,resulting in a decrease in their effective specific surface area and less susceptibility to electrolyte infiltration,their electrochemical performance is much lower than expected.To solve the above problems,in this article,we prepared novel three-dimensional structures with controllable structure and morphology using graphene and graphdiyne as carbon-based materials.The specific research content is as follows:（1）A three-dimensional carbon composite material Mn O₂/GO/PPy with adjustable mesoporous structures were prepared by adjusting the content of pyrrole using a simple hydrothermal method.By adjusting the pore size of three-dimensional graphene nanocomposites,the effective electrochemical specific surface area of the composite material was increased.It is found that Mn O₂/GO/PPy-5（pyrrole content:5μL）nanocomposites have small average pore size,high pore volume,and high specific surface area,with suitable micro mesoporous structure and pore size distribution.To further improve the electrochemical performance of the composite,Ag/Mn O₂/GO/PPy-5nanocomposites were synthesized by modifying Mn O₂/GO/PPy-5 nanocomposites with silver nanoparticles.The prepared Ag/Mn O₂/GO/PPy-5 nanocomposite material has excellent specific capacitance(C=474.3 F g^-1,5 m V s^-1)and high cycling stability（with an efficiency of up to 105.3%after 10000 charge-discharge cycles）.The control of the micro-mesoporous structure can make the ion transport more convenient,promote ion exchange,and adapt to the volume expansion and contraction in the charge/discharge process,thus improving the specific capacitance and cycle stability.Moreover,the evenly distributed manganese dioxide and silver nanoparticles in the nanocomposites provide more redox reaction sites and better conductivity.（2）New three-dimensional porous composite materials,graphdiyne-carbon nanotubes（GDY-CNTs）and graphdiyne-nitrogen-doped carbon nanotubes（GDY-NCNTs）,were prepared with ethylene and pyridine as carbon sources by using CVD in-situ growth method.It is found that CNTs in GDY-CNTs composite materials grow uniformly and vertically on the surface of GDY,and the growth process of CNTs follows the top growth mechanism.The top growth structure can promote electron transfer at the interface.And the doping of nitrogen atoms in GDY-NCNTs composite materials leads to changes in the geometric structure of CNTs,increasing surface defects.The specific capacitance of GDY-NCNTs composite material is as high as 679 F g^-1 at a scanning speed of 2 m Vs^-1,which is much higher than that of pure GDY material,pure CNTs material,and GDY-CNTs composite material.The capacity retention rate of GDY-NCNTs composite material is still115.5%after 10000 cycles.The three-dimensional porous structure in GDY-CNTs and GDY-NCNTs composites is beneficial to increase the number of active sites,promote the ion transport rate,adapt to the volume expansion and contraction in the charge discharge process,and thus improve the electrochemical performance.