Preparation And Electrochemical Performance Of Nitrogen-containing Carbon Materials Based On Waste Textile Materials

Nowadays energy and environment have become two major issues for sustainable social development.Energy is the main force driving economic and social development,while fossil fuels still occupied the dominant position of all the energy forms.With the over exploitation and utilization of fossil fuels,the greenhouse effect and environmental pollution are getting increasingly deteriorated.Therefore,the development of new and renewable clean energy is becoming significantly important for human survival and development.Biomass energy,stored in the waste biomass,is one of the most important renewable energies but is far from fully used.The utilization rate of biomass energy is quite low.China is a large textile country and produces a large amount of waste textiles each year.Currently,most of the carbon-rich waste textiles are disposed of by landfill or incineration.This treatment method not only wastes resources but also pollutes the environment.In addition to landfill and incineration,waste biomass can also be prepared carbon materials.This article uses the molten salt method to convert waste textiles into functional carbon materials.The specific research contents and results are as follows:1)Transformation of biomass into nitrogen-doped carbon materials has been considered as effective and affordable route for energy generation and conversion.Wool fiber,as an abundant renewable biomass,contains plentiful nitrogen element.Here,nitrogen-doped porous carbon derived from wool fiber by molten salt carbonization method has been realized in 700 ^oC LiCl-KCl melt.The wool fiber-derived carbon via molten salt carbonization?WFC-MSC?with honey comb-like structure has a specific surface area of 787.079 m² g^-11 as well as a nitrogen content of 2.6 wt.%.Using this nitrogen-doped carbon as electrode materials for supercapacitor,high specific capacitance of 318.2 F·g^-1 at 0.25 A·g^-1and good high-rate capability are achieved.The stable cycling performance with specific capacitance of 210 F·g^-1 after 5000 cycles at5 A·g^-1 is realized.Moreover,WFC-MSC based symmetric supercapacitor possesses high specific energy of 20.2 Wh kg^-1 with a power density of 202 W kg^-1 operated a wide voltage range of 1.8 V in aqueous neutral Na2SO4 electrolyte.These results highlight the merits of the molten salt carbonization of wool fiber in producing nitrogen-doped porous carbon,and suggest its prospect for application in supercapacitors.2)Nitrogen-doping is considered to be a promising way to improve the performance of activated carbon-based supercapacitors.Since many of the biomass itself does not contain nitrogen,or contain traces of nitrogen,so you need to add additional nitrogen source in order to achieve the objective of nitrogen–doped.In this chapter,denim-based nitrogen-doped carbon material?NAPC-5?prepared in 800?LiCl-KCl mixed molten salt system has high specific surface area?1791 m²/g??high nitrogen content?7.692 wt.%?and nano-random morphology,using denim as precursor and melamine as nitrogen source.In 6 M KOH electrolyte,NAPC-5 electrode has a capacitance as high as 331.5 F·g^-1 at 0.25 A·g^-1 and remains 240 F·g^-1 at 10.0 A·g^-1.Besides,NAPC-5 electrode exhibits good cycling stability,with capacitance retention of 95.8%after 5000 cycles at 5.0 A·g^-1.At the same time,some carbon-based materials were assembled into lithium batteries,and their specific capacity was investigated,NAPC-5 sample has a capacity as high as 405.09 mAh·g^-1,which is more suitable as battery material.The simple synthesis route and high electrochemical performance of the NAPC-5 show great potential in supercapacitor and battery application.3)Linen-based carbon fiber materials were prepared by pre-oxidation at 250?for 1h and pyrolysis at 700?for 120 min using waste linen cloth precursors.The experimental results show that the linen based-carbon fiber possesses complete fibrous structure.The BET surface area is 737.8 m²·g^-1 and the pore volume is 0.41 cm³·g^-1.When the linen-based carbon fiber material is fabricated into electrode materials for electrochemical test,the best specific capacitance at a current density of 0.25 A·g^-1 is185 F·g^-1.