Preparation And Electrochemical Energy Storage Performance Of Porous Carbon Materials Based On Expansion Reaction

In recent years,with the increasing number of people in the world,the per capita economic living standard has been continuously improved,the available energy on the earth has been decreasing,and the environment has gradually deteriorated.This phenomenon has caused widespread concern.Therefore,the search for a green,sustainable,efficient and fast energy storage component has become the most important thing for human survival and development.As a new type of energy storage device,supercapacitor has many advantages,such as high energy density,environmental protection,wide operating temperature range,long service life,instantaneous high current discharge and so on.Therefore,it has attracted more and more attention.As an important part of supercapacitors,the electrochemical performance of supercapacitors is largely determined by the electrode materials.Therefore,we must find new and good electrode materials with high capacitance.Among them,carbon materials are widely used in the preparation of high performance electrode materials because of their high specific surface area,good conductivity,simple preparation process,adjustable microstructure,various forms and good chemical stability.Inspired by the classical chemical experiment"Pharaoh's Snake",porous carbon materials were prepared by dehydration and expansion of expired sucrose powder with concentrated sulfuric acid.Bacterial cellulose was added into the porous carbon materials to prepare composite porous carbon materials,and porous carbon materials were prepared by combustion and expansion of sucrose powder.The microstructures,properties and electrochemical properties of the prepared carbon materials were studied by means of SEM,TEM,XRD,XPS,BET,Raman and electrochemical tests.The main research contents are as follows:Porous precursors were obtained by the reaction of expired sucrose powder with concentrated sulfuric acid.Porous carbon materials were prepared by pyrolysis of KOH as activator and argon as protective gas at high temperature.The porous carbon materials have abundant porous structure and high specific surface area(1698 m² g^-1).The results of electrochemical tests show that the specific capacitance of carbon materials activated by high temperature pyrolysis at 800°C is 270 F g^-11 at 1 A g^-1current density in 6 M KOH electrolyte,and it shows excellent cyclic stability.Compared with the materials prepared without the over-expansion reaction step,the materials prepared by the expansion reaction step have larger specific surface area and better electrochemical properties.This further shows that the preparation of porous carbon materials by this method is successful.The porous carbon material?HZTC?prepared by concentrated sulfuric acid pretreatment and the biomass bacterial cellulose?BC?with three-dimensional network space structure were mixed as the carbon source,KOH as the activator,and argon as the protective gas.Under the condition of high temperature pyrolysis activation,the three-dimensional mesh porous carbon material?XHZTC-800-n?with high specific surface area was successfully prepared.Results show that the sample has the amorphous structure,and presents the communication of three dimensional network spatial structure,the BET test results show that the specific surface area of the material up to 1910 m² g^-1,and it is mainly micro mesopore structure,which will be conducive to the electrolyte ions quickly migration and the formation of electric double layer capacitors,on the electrochemical performance of ascension to provide effective help.Cyclic voltammetry test and constant current charge-discharge test show that the material has good reversibility,good charge-discharge efficiency and good double-layer capacitance behavior.In the 6 M KOH electrolyte environment,with the current density of 1 A g^-1,XHZTC-800-2 has A specific capacitance of up to309 F g^-1.After 5000 charge and discharge cycles,its capacitance retention rate is up to 96%.Using expired sucrose powder as carbon source and NaHCO₃ as chemical foaming agent,mixing and igniting it,using sodium carbonate sodium to be thermally decomposed to generate a large amount of carbon dioxide gas,can make sucrose powder transform into a loose skeleton under the action of carbon dioxide gas.The"snake"porous carbon precursor,using argon as a shielding gas and KOH as an activator,was successfully pyrolyzed under high temperature conditions to produce a porous carbon material BZTC-T.The prepared porous carbon material is amorphous carbon with large specific surface area and reasonable pore size distribution.When the pyrolysis temperature is 800°C,the specific surface area is as high as 3540 m² g^-1.Cyclic voltammetry test and constant current charge and discharge test results show that the material cycle is reversible,has good charge and discharge efficiency,and exhibits good double layer capacitance behavior.It is found that BZTC-800 has the best through temperature gradient experiment.The electrochemical performance of the 6 M KOH electrolyte has a specific capacitance of up to 289 F g^-11 at a current density of 1 A g^-1,and its capacitance retention rate is as high as 95.8%after 5000charge and discharge cycles,thus indicating that the material has good cycle stability.Compared with the porous carbon material prepared by the high-temperature pyrolysis method directly using the ordinary sucrose powder as a carbon source,the porous carbon material prepared by the"burning sugar"step is added,and the surface area and electrochemical performance are more excellent characteristic.