Design,Preparation And Electrochemical Performance Of Biomass Derived Carbon

Biomass has the characteristics of renewable,abundant,and low cost.Using biomass as carbon source for the preparation of biomass-based carbon materials can effectively use resources,increase the added value of biomass,and reduce the environmental pollution caused by direct burning of biomass waste.It has the characteristics of energy saving,value-added,and eco-friendly.On the basis of its unique structure and abundant element content,biomass provides favorable conditions for the preparation of functionalized carbon materials.The pretreatment methods,the amount of activator used,and the activation temperature have great influences on the biomass based carbon materials.In this paper,four kinds of biomass and waste resources in Xinjiang Uygur Autonomous Region of China were selected as the precursors of carbon materials.Different carbon materials were synthesized through different methods.The corresponding characteristics of these carbon materials have been thoroughly investigated.1.Tobacco was used as the precursor of biomass-derived carbon.Tobacco based porous carbon was prepared through pre-hydrothermal reaction and carbonization of tobacco.It was further activated by KOH to obtain tobacco based activated carbon.The result shows that the process of KOH activation can improve the specific surface area,micropore distribution,and oxygen-containing functional groups of the activated carbon.These features make tobacco derived activated carbon displayed a specific capacitance of 148 F g^-11 in 6 mol/L KOH electrolyte at a current density of 0.5 A g^-1by three electrode system,which is four times to tobacco based porous carbon.2.Cotton seed husk was used as the precursor of biomass-derived carbon.It was stirred with KOH solution,dried,and further pyrolyzed at different temperature to obtain nitrogen doped 3D honeycomb-liked porous carbon.The obtained carbon had a nitrogen content of2.56 at.%,in addition to a high surface area of 1694.1 m²g^-1when the pyrolyzed temperature was 700 ^oC.Owing these distinct features,the obtained carbon achieved a high specific capacitance of 238 F g^-1at a current density of 0.5 A g^-1and retained a capacitance of200 F g^-1at 20 A g^-1in 6 mol/L KOH electrolyte by three electrode system.The capacitance retention was 84.03%.3.Elm flower was also used as the precursor of biomass-derived carbon.N,S-Doped activated carbon was directly prepared via a facile and cost-efficient hydrothermal reaction,followed by KOH activation of elm flower derived biomass.Through adjusting the mass ratio of KOH to the prehydrothermal carbonized elm flowers,the resultant N,S-doped activate carbon possesses a high specific surface area of 2048.6 m² g^-1,moderate pore volume,and abundant N and S contents（2.21 and 6.06 at.%,respectively）.And the as-synthesized N,S-doped activated carbon electrodes exhibited a high specific capacitance(275 F g^-11 at a current density of 1 A g^-11 and 216 F g^-11 at a current density of 20 A g^-1).The capacitance retention was 75.54%.4.Hydrothermal carbonization followed by chemical activation is utilized to convert actual dye wastewater togther with glucose into high graphitized carbon.The as synthesized carbon displayed a specific capacitance of 273 F g^-11 at a current density of 1 A g^-11 and retained a capacitance of 200 F g^-11 at 20 A g^-11 in 6 mol/L KOH electrolyte by three electrode system.The capacitance retention was 73.26%.This is a direct result of its high surface area(1734.4 m² g^-1)and moderate N and S contents（2.12 and 0.64 at.%,respectively）,which actually improve the electrochemical performances.