Preparation Of Self-doped Porous Carbon Materials Based On Biomass And Their Electrochemical Properties

In order to reduce the transition dependence on fossil energy,more and more new energy sources have begun to enter people's vision,including wind energy,solar energy,tidal energy and hydrogen energy,which have been successfully developed.At the same time,devices with high efficiency of energy conversion and energy storage have also attracted wide attention.The most well-known is supercapacitor,which is famous for its high power density and long cycle life.As an advanced energy storage device,supercapacitors often use carbon-based materials with low cost and high specific surface area as the preferred electrode materials.In recent years,carbon materials derived from biomass have attracted more and more attention because of their low cost,environmental protection and high efficiency.In this paper,three common biomass materials were selected as raw materials,and self-doped porous carbon materials with high specific surface area and well-developed pore structure were prepared by simple process.They were used as electrode materials for supercapacitors,showing excellent electrochemical performance.The main contents are as follows:?1?Three-dimensional interconnected honeycomb-like porous carbon materials with high specific surface area(1484 m² g^-1),layered porosities and heteroatom self-doping were successfully prepared by one-step carbonization using cheap seeds of green bristlegrass as precursors.The specific capacitance of the materials used as electrode materials for double layer supercapacitors?EDLCs?was as high as 391 F g^-1(current density at 0.5 A g^-1),and the retention rate of the capacitors was as high as 97.2%.after 10,000 cycles.The symmetric supercapacitor?SSC?device can provide 500 W kg-1 power density and 20.15 Wh kg^-1 energy density with 1 M Na2SO4 electrolyte and 2.0 V voltage window.In addition,it shows excellent rate performance,cycle stability and high Coulomb efficiency.?2?High specific surface area and N,O,S polyatomic self-doped porous carbon materials were prepared by simple carbonization in KOH solution.When the current density was 0.5A g^-1,the mass specific capacitance was 356 F g^-1,and the retention rate of capacitance was 95%after 10000 cycles.The SSC devices assembled by the device show excellent rate performance,reversible cycle stability and high power density and energy density.?3?Silkworm eggshells were carbonized by two different methods.The results showed that the carbon materials prepared by acid-hydrothermal pretreatment had larger specific surface area and abundant pore size structure.They were used as electrode materials for supercapacitors,and the specific capacitance was as high as313 F g^-1 at 0.5 A g^-1 current density.The supercapacitor device has good cycle stability?the initial capacitance retention rate is 91%after 10000 cycles?,and can also provide 500 W kg^-1 power density and 17.42 Wh kg^-1 energy density.