The Preparation Of Chitosan Carbon@Co-Based Electrode Materials And Supercapacitor Performance Research

In recent years,supercapacitors have attracted significant attention,mainly due to their huge capacitance,high power density,long lifecycle,and fast speed at charge and discharge.What make supercapacitors have a special advantage in energy storage and power output.Activated carbon material is rich in raw materials,ease of synthesis,and environment-friendly.As the result,activated carbon is the most successful commercial electrode material in supercapacitors.However,conventional activated carbon materials has a terrible series resistance,does not apply to large current charge and discharge;it has high specific surface area,but pore size distribution unevenly(there are a lot of micropores,electrolyte can not enter the interior).Therefore,the specific capacitance can only achieve 10% to 20% of the theoretical value.Studies have shown that nitrogen-doped will help improve the electrochemical properties of the carbon material.Chitosan is a byproduct of food processing,which is rich in nitrogen element.A porous nitrogen-doped carbon were prepared by carbonizing chitosan under nitrogen and at different temperatures(700 ?,800 ?,900 ?).Chitosan-based carbon which obtained at 800 ?,exhibited the best electrochemical performance.The specific capacitance of the first cycle is 64.42 F/g in 2M KOH and with cyclic voltammetry scan rate of 1mV/s.the specific capacitance maintaine at97.49% after 20 cycles,showing good cycle performance.Preparation of carbon-based composite material is also an effective method to improve the electrochemical properties of the material.chitosan@Co(NO3)2 xerogels has prepared by taking advantage of hydroxyl and amino groups which exist in chitosan molecular chain and can coordinate with metal ions.Xerogel complete carbonation and reduction reactions by one-step.carbon@Co-based composite electrode material is prepared by one-step.Xerogel complete carbonation and reduction reactions at same time under nitrogen.Due to high temperature of the preparation conditions,Co mainly exist in the form of cubic crystal.XRD and Raman show that Co(NO3)2 will make the composite material of carbon toward amorphous.BET analysis indicate that a certain amount of Co(NO3)2,can improve the pore structure of the composite material,improve the specific surface area,and it is good for the electrochemical properties of the electrode material.When the parameter of Co(NO3)2 is 10%,the composite material surface area reache 194.37m2/g.The first cycle specific capacitance is 102.29 F/g in 2M KOH and with cyclic voltammetry scan rate of 1mV / s.The capacitance maintaine at97.75% after 20 cycles.To further increase the capacitance of the composite material,amorphous Co has be synthesized and drop on self-made chitosan-based carbon through NaBH4 reduction of CoCl2.The reaction conditions is at low temperature.Carbon@Co–based composite electrode material obtained by two-step process.Co is mainly in amorphous form,which is more conducive to the electrode reaction occurs with depth.Cyclic voltammetry showed that the composite material prepared under low temperatures,exhibit Pseudocapacitance characteristic of cobalt.the specific capacitance also improve to 124.45 F/g and is maintained at 98.5% after 20 cycles in 2M KOH and with cyclic voltammetry scan rate of 1mV/s.