Construction And Capacitance Properties Of Biomass Nano-carbon Based Materials

Growing energy resources consumption and corresponding environment crisis have sparked an ever increasing and urgent demand for clean,advanced and renewable energy storage and conversion systems.Among multifarious energy storage facilities,supercapacitors have raised unprecedented concern in both industry and academia over the past decades principally owing to their ultrahigh power density(¹0 kW kg^-1),rapid chargeing/discharging rates,long cycling lifespan?>100000cycles?,low operating/maintenance cost and safe operating environment.The gap of power between rechargeable batteries and traditional capacitors is greatly filled by supercapacitors,which can display larger power explosion than batteries and higher energy than traditional capacitors due to their rapid adsorption/desorption energy storage mechanism.Despite numerous merits of supercapacitors,its relatively low energy density impedes widespread applications.Motivated by the various nanostructure and great chemical stability,carbon materials have occupied a crucial and irreplaceable status in the fields of supercapacitor.However,non-renewable precursors,highly corrosive reagents,complicated fabrication processes and high cost of traditional carbon materials impedes their large-scale production.In recent years,renewable heteroatom-rich biomasses and their derivatives have been considered as ideal precursors to prepare heteroatom-doped hierarchical porous carbon because of their natural abundance,low cost,easy availability and eco-friendliness.In this thesis,various biomass materials were selected as the precursors,and a series of high-performance biomass carbon-based materials were obtained through a simple activation/pyrolyzation process.The strucutre,microscopic characteristics and electrochemical properties of the materials were systematically investigated.The main research contents and results are as follows:1.Waste protein-rich pig nails were used to prepare nitrogen-doped hierarchical porous carbon by facile KOH activation.The microtopography and electrochemical property were investigated by tuning the weight ratio of KOH/sample.The nitrogen-doped hierarchical porous carbon?NHPC-1?obtained at weight ratio of 1:1exhibits the largest specific surface area(2569 m² g^-1)with 3D porous carbon network,which are beneficial to transmission of ion/electron.Besides,the nitrogen functional groups of the NHPC-1?2.8 at.%?also contributes to improve electrochemical activity.As a result,the prepared NHPC-1 exhibits high specific capacitance of 231 F g^-1 at 1A g^-1,superior retention of 98%after 5000 cycles as well.Additionally,assembled symmetric device using NHPC-1 as electrodes possesses high energy density of 7 Wh kg^-1 at the power density of 500 W kg^-1.Our study suggests that waste pig nails can act as low-cost and renewable carbon precursors for high performance supercapacitor.2.Carbon materials have aroused extensive attention as electrode materials for supercapacitor,especially those with 3D conductive network structure.Herein,the nitrogen doped hierarchical porous carbon derived from pigskin was prepared by a facile activation/pyrolysis process.Specifically,the nitrogen doped hierarchical porous carbon possesses open ion-accessible channels.The designed carbon materials exhibit remarkable specific capacitance of 287.1 F g^-1 at 1 A g^-11 and admirable capacitance retention of 99.0%after 10000 cycles.Noticeably,the assembled symmetric supercapacitor displays a high energy density of 43.0 Wh kg^-1 at the power density of 875.0 W kg^-11 using EMIMBF₄ ionic liquid electrolyte.This low-cost porous carbon materials derived from biomass source shows great promise for potential applications in the fields of energy storage and conversion device.3.The nitrogen doped hierarchical porous carbon was derived from soybean dreg through KOH activation for high performance supercapacitor.When carbonized at800 ^oC,the prepared carbon shows a high ion-accessible surface(1837.26 m² g^-1)and a high level of micropores(0.71 cm³ g^-1),which are beneficial for large-scale ion storage and high-speed ion transport.In addition,high contents of nitrogen?1.58 at.%?can induce the contribution of faradaic pseudocapacitance for during electrochemical reaction process.The obtained carbon displays a superior specific capacity of 321.1 F g^-1 at 1 A g^-1.Notably,an excellent energy density can reach as high as 22.1 Wh kg^-1at the power density of 875.0 W kg^-11 in two-electrode system using EMIMBF₄electrolyte.This green,renewable and eco-friendly biomass porous carbon might be widely used in the fields of energy conversion device for now and in the foreseeable future4.Heteroatom-doped hierarchical porous carbon materials have aroused widespread concern in the field of supercapacitors due to their effective ion-accessiblesurface,abundant porosity and low manufacturing cost.However,its relatively poor electric conductivity might not completely meet the requirements of comprehensive application of supercapacitor.Herein,to further promote conductivity of porous carbon,an all carbon nanocomposite was successfully fabricated by implanting carbon nanotubes?CNTs?into the surface and edge of nitrogen doped hierarchical porous carbon?NHPC?.The CNTs endow the composites with high conductivity and connect porous carbons to each other,which renders rapid ion transfer and store during charge/discharge process.Benefiting from strong bonding effects due to plentiful heteroatom functional groups,the nitrogen-doped hierarchical porous carbon/CNT hybrid exhibits considerable charge transport ability and superior specific capacitance of 293.1 F g^-1 at current density of 1 A g^-1,high rate capability of207.0 F g^-1 at 30 A g^-1.Furthermore,the assembled symmetric supercapacitor displays a high energy density of 27.46 Wh kg^-1 at the power density of 874.98 W kg^-1.The unique hierarchical three-dimensional hybrid structure provides a novel way todevelop conductive carbon electrode materials for advanced supercapacitors.