Preparation And Capacitive Performance Research Of Nitrogen-doped Hierarchical Porous Carbon Electrode Material

Casting about for reliable,continuable and efficient energy source forms free of pollution emission is a prerequisite resolvent to cope with the increasing energy shortage and concomitant environmental pressure.Integrating characteristic of high-power density and long cyclic life and accompanying the property of wide working temperature range,good safety and stability,supercapacitors with high energy storage have aroused enormous attention.The advantages of carbon materials contain rich sources,inexpensive,non-toxic,easy processing,high specific surface area,fine electrical conductivity,good chemical stability and so on.Thus,carbon material has been widely used.Although the carbon material has a relatively high specific surface area,the pore size distribution is not very reasonable,which greatly limits the improvement of specific capacitance.Thus,a carbon material with more desirable distribution of pore structure remains to be further studied.In this paper,the main research objective is to prepare hierarchical porous carbons,combining with nitrogen doping,template,chemical activation and other ways so as to prepare hierarchical porous nitrogen doping activated carbon material successfully.The main research contents are as follows:Polyacrylonitrile?PAN?as the main carbon material and polymethyl methacrylate?PMMA?/tetraethyl orthosilicate?TEOS?as dual templates,different mass fractions of thermoplastic polyurethane?TPU?acted as nitrogen-doped material.Preparing carbon nanofibers by electrospinning technique,and then nanofibers have been carbonized at a high temperature to remove the soft template PMMA,using hydrofluoric acid?HF?to remove the hard template TEOS,which can obtain nitrogen-doped porous carbons under the conditions without any activation process.Conducting associated physical characterization and electrochemical measurements.N2 adsorption-desorption measurement indicates the sample?labeled PT10?containing 10 wt.% TPU possesses the large specific surface area of 1126 m2 g-1 and holds volume value of 0.424 cm3 g-1.The electrochemical measurements show PT10 sample obtains specific capacitances of 207,203 and 198 F g-1 at the current density of 0.2,0.5 and 1.0 A g-1,respectively.Moreover,the capacity faded lower than 5% after 8000 cycles of charging and discharging,indicating its excellent electrochemical stability.Based on the previous study,PAN acted as carbon precursor and PMMA acted as single template,selecting the best TPU quality doping fraction.Potassium hydroxide?KOH?acted as activator to prepare hierarchical porous nitrogen doping activated carbon materials.Exploring different activation mass ratios?KOH and carbon materials ratio?of electrode materials and conducting related characterization.N2 adsorption-desorption measurement indicates the sample?labeled CNFA4?with the activation mass ratio for 4 possesses the large specific surface area of 2217 m2 g-1 and holds high volume value of 1.443 cm3 g-1 as well as hierarchical porous structure.The electrochemical measurements show CNFA4 sample obtains specific capacitances of 255,238,230,215 and 198 F g-1 at the current density of 0.2,0.5,1.0,5.0 and 10 A g-1,severally.Furthermore,the sample material possesses good rate capability and the specific capacitance decrease a little during 8000 cycles.Assembling supercapacitors with CNFA4 electrode material.Using 6 mol/L mol/L KOH,1 mol/L H2SO4,0.5 mol/L K₂SO₄ as electrolyte respectively and exploring the electrochemical performances in three different electrolytes.Studies have shown that supercapacitors possesse the best electrochemical performance in KOH electrolyte.