Synthesis And Electrochemical Performance Of Chitin Based Nitrogen-doped Porous Carbon

Currently,developing environmentally friendly sustainable energy resources is still a great challenge for global researchers.For achieving this goal,supercapacitors have been regarded as one of the most promising electrochemical energy sources for energy storage and conversion devices because of its great advantages including rapid charging-discharging rates,high power density,long cycle life,wide range of suitable temperature and so on.And it has been successfully applied in communication,transportation,energy and other fields.The electrode material acts as an important part of supercapacitors,and its composition and structure directly affect the performance of supercapacitor.Carbon material is the best commercial electrode material up to now,because of its plentiful raw materials,low cost and high specific surface area.And N-doped carbon materials have vast development space in electrochemistry application due to the existence of electron-rich nitrogen and the lone pair of electrons.In this work,A systematic study was carried out on the structure-effect relationship between the controllable preparation of rich N-doped porous carbon materials and electrochemical performance for energy storage by using chitin as precursor.Thermal gravimetric analysis was used to obtain the thermal decomposition behavior of chitin.X-ray photoelectron spectroscopy analysis was performed to investigate the surface chemistry and funcational groups on the carbons.X ray diffraction and scanning electron microscopy were applied to characterize the crystalline structure and surface morphology for resultant carbons,respectively.In addition,cyclic voltammetry,galvanostatic charge discharge and electrochemical impedance spectroscopy were conducted on a three and symmetrical two electrode systems using 6 M KOH solution as electrolyte in order to investigate the electrochemical performance of the as-made N-doped porous carbon materials as electrode for supercapacitors.The main contents of this thesis are as follows:?1?CSC-x?x=0.5?1?2?3?were prepared througha facile process via pre-carbonization of demineralized cicada slough followed by KOH activation,cicada slough was employed as carbon and nitrogen source.The results show that KOH:CSC=2?CSC-2?has specific surface area(as high as 1745 m² g^-1).CSC-2exhibits the highest specific capacitance(266.5 F g^-1at current density of 0.5 A g^-1)and excellent rate capability(196.2 F g^-1remained at 20 A g^-1)and cycle durability(the specific capacity retention is 92.7%after 5000^thcycle).In addition,CSC-2 based symmetrical device at 5 A g^-1possesses the desirable energy density and power density of about 15.97 W h kg^-1and 5000 W kg^-11 in KOH aqueous electrolyte.?2?In thi spart,N-doped carbon materials were prepared through a facile strategy via pyrolysis of a mixture containing chitin and ammonium salt.The ammonium salt we use are mainly NH₄HCO₃,?NH₄?₂SO₄ and NH₄Cl.the utilization of NH₄Cl as porogen shows the best electrochemical capacitive performance in this section might due to the decomposition temperature of ammonium chloride is close to the decomposition temperature of chitin.Chitin was employed as carbon source,while ammonium chloride acts as both the nitrogen dopant and porogen?NH₃?.The as-made NC-NH₄Cl-1 pyrolysized at the NH₄Cl-to-chitin weight ratio of 1 exhibited the highest specific capacitance(274 F g^-1at a current density of 1 A g^-1)and good cycle stability.Moreover,NC-NH₄Cl-1 based symmetrical device at 10 A g^-1possesses the desirable energy density and power density of about 11.11 W h kg^-1 and 10000 W kg^-1.