Preparation And Optimization Of Biomass-based Multi-porous Carbon Materials And Its Supercapacitor Performance

In recent years,sustainable development has become a new trend.Fortunately,among various porous carbon materials,biomass-derived porous carbon materials have gradually become a new direction in the research of supercapacitor electrode materials,due to they not only have good electrical conductivity,but also have abundant sources and low preparation costs.Among them,converting waste biomass into high-performance energy storage materials with hierarchical porous structures can accord with the subject of energy sustainable development.In this paper,the waste wood biomass was used as a carbon source to prepare porous carbon materials and explore its performance for supercapacitors.The details are as follows:We prepared porous carbon materials with different pore structures by four strategies using wasted platanus acerifolia seeds?PS?as carbon sources.By comparing pure pyrolysis,pyrolysis-activation,hydrothermal-pyrolysis method and the alkaline hydrothermal-pyrolysis process,it was found that the H/K-PSC800 sample prepared by alkaline hydrothermal-pyrolysis process has optimal porous structure parameters.This is because that during the alkaline hydrothermal treatment,KOH can accelerate the thermal exfoliation and degradation of lignin and hemicellulose in the raw PS.More importantly,the KOH will remain in the interior of the seed,and it will act as an activator in the subsequent high temperature carbonization process.Electrochemical characterization of the four porous carbon materials was demonstrated,which further proved that the electrochemical property of the sample prepared by the alkaline hydrothermal-pyrolysis process was also the best.It can be seen that the alkaline hydrothermal-pyrolysis process is a preferred method for preparing a PS-based porous carbon material,wherein the alkaline hydrothermal pretreatment is critical for the structural formation and evolution of the prepared porous carbon.After determining the alkaline hydrothermal-pyrolysis,the subject further explored the effects of different carbonization temperatures on the pore structure of porous carbon materials H/K-PSCX?X=700,800,900?and the performance of supercapacitors were also investigated.It was found that the H/K-PSC800 sample has a very large specific surface area(1540.6 m² g^-1)and a three-dimensional mesh sponge structure coexisting with micropore,mesoporous and macroporous structure,and its specific surface area is much larger than H/K-PSC700 sample(1360.9 m² g^-1)and H/K-PSC900 sample(1312.8 m² g^-1).Moreover,the carbon content of H/K-PSC800 is as high as 91.7%,which makes its conductivity is also very good.The rational structure of H/K-PSC800 resulted in excellent specific capacitance?315 F g^-11 at 1.0 A g^-11 in an aqueous electrolyte?,good capacity retention?the specific capacitance decreases by 28.9%when the current density increases 10 times?and high cycling stability?93%of its initial capacitance after 2000 cycles?,and the assembled supercapacitor has excellent energy density and power density(30.9 Wh kg^-11 at a low power density of 500 W kg^-1).The pine-based porous chips were used as raw materials,and the preparation of porous carbon was carried out by the alkaline hydrothermal-pyrolysis method again.It has been found that the amount of alkali has a certain influence on the pre-treatment and subsequent activation process of the material.Only when the amount of alkali reaches a certain value will the pine structure be destroyed.Moreover,with the increase of the amount of alkali,the structure inside the pine is destroyed more and more severely,and the cellulose also undergoes a crystal transformation.The finally obtained porous carbon material H/K-PC800-5 has the best pore structure and excellent electrical performance.H/K-PC800-5 has the best pore structure and excellent electrical conductivity.H/K-PC800-5 also has excellent specific capacitance?363 F g^-11 at 1.0 A g^-11 in an aqueous electrolyte?,and the assembled supercapacitor also has excellent specific capacitance(254.1 F g^-11 at 1.0 A g^-1)and excellent capacity retention and excellent cycle stability?92%of its initial capacitance after 2000 cycles?.