Preparation And Electrochemical Performance Of Biomass Based Electrode Materials For Supercapacitors

Biomass-based carbon materials not only satisfy the demand of the renewability and the effective utilization of resources,but also show a series of advantages,such as high specific surface area,adjustable pore size and modifiable surface.Thus,biomass-based carbon materials have made great achievements in the field of electrode materials for supercapacitors,due to the low production cost,high benefit,large-scale processing and applications.In addition,biomass materials are rich in oxygen-containing functional groups and heteroatoms,which can be doped in situ to provide pseudocapacitors and improve storage performance.What’s more,they also have high surface area by adjusting the pore size distribution and the porous structures through template method or activation method.Therefore,the synergistic effects of pseudocapacitance and double layer capacitance can significantly enhance the electrochemical properties of the prepared carbon materials.The main reaseach concents of this paper are as follows:1.Nitrogen and oxygen co-doped glucose-based porous carbon materials（NGPC-0.50）were successfully synthesized using ethylenediamine as nitrogen source and silica as hard template.The effects of carbonization temperatures and hard template on the properties of the material were systematically investigated through a series of characterization tests.The specific surface area of the NGPC-0.50 is 460.93m² g^-1 and the specific capacitance is 313 F g^-1 at a current density of 1.0 A g^-1.Moreover,the specific capacitance remains 144 F g^-1 at 10 A g^-1,indicating its good rate capability.2.Protein-based porous carbons（PPC600-1:2）with excellent properties were prepared at the optimum activation temperature（600 ^oC）and activation ratio（1:2）.The contents of nitrogen,oxygen and sulfur are 15.29,12.21 and 0.71 at.%,respectively.The PPC600-1:2 exhibits aboundant porous structures produced by activation and high specific surface area of 1117 m² g^-1.The specific capacitance of PPC600-1:2 is 336 F g^-11 at a current density of 1 A g^-1,and it can persist 173 F g^-1 at 10 A g^-1,indicating the good rate capability.At the same time,the cycling stability of the sample is 83%after10000 cycles at 10 A g^-1.3.Chitosan,a renewable biomass derivative,was used as electrode material with a facile pyrolysis and activation process for supercapacitors.The sample obtained at the best powder/KOH ratio of 1:1 exhibits meaningful structural characteristics:optimized interconnected hierarchical pore structures and high specific surface area(863.58 m² g^-1).It possesses excellent capacitive property with high specific capacitance of 310 F g^-1 in 6 mol L^-1 KOH electrolyte at a current density of 1 A g^-1,and enhanced rate capability(231 F g^-1 can be retained at 10 A g^-1).Additionally,it shows excellent capacity retention of 80%after 10000 cycles at 10 A g^-1.4.The nitrogen-doped porous carbon nanosheets（NPCN-0.5）with novel morphology were prepared by a facile solution blending method using chitosan and gelatin.Gelatin changes the morphology of the chitosan-derived carbon materials and formes a tangerine pith-like nanowire,which can be distributed more evenly on the surface of the sheet,and increases heteroatom content（5.75 at.%of nitrogen,15.04at.%of oxygen）.With the help of KHCO₃,a large number of interconnected pores are formed,which greatly increase the specific surface area(927.17 m² g^-1)of carbon materials.The NPCN-0.5 displays wonderful capacitive performance of 331 F g^-1 at a current density of 1 A g^-1,high retention of 73%at 10 A g^-1 and excellent capacity stability of 90%after 10000 cycles at 10 A g^-1.Additionally,the chitosan-derived hybrid porous carbon shows remarkable energy density of 34 W h Kg^-1 with the power density of 900 W Kg^-1,superior to majority of the commercial devices.