| Supercapacitors have become a new type of energy storage device that have been extensively studied because of its advantages of high power density,long cycle life,high charge/discharge efficiency,maintenance-free,and environmental friendly.Among the components of the supercapacitor,the electrode material is the main factor that determines its electrochemical performance.Therefore,the study on the electrode material has become a hotspot in this field.Activated carbon is the earliest electrode material used in the preparation of supercapacitors.However,some challenges such as some invalid pore structure,low specific capacitance and high cost of activated carbon limit its electrochemical performance.Therefore,based on the biomass-based raw materials,this paper studied the effect of the NaOH pretreatment time and activation process conditions on the pore structure of activated carbon.High specific surface area and high mesoporous carbon materials were prepared,and the activated carbon is applied to the electrode material of the supercapacitor.In addition,in order to increase the specific capacitance of the activated carbon electrode,activated carbon loaded NIC02O4 composite electrode was prepared,and the electrochemical performance of the composite material was studied.The main conclusions are presented below:(1)Lignin removal from corncob residues by NaOH pretreatment produce high mesoporous rate,high surface area activated carbon and may form pore gallery making it easier to contact with activator.As a consequence,activate carbon with high specific surface area and mesoporous rate was obtained.The developed pore structure and high specific surface area was achieved when corncob was pretreated by NaOH for 4 hours under a impregnation ratio of 4:1,activation temperature at 500OC.The surface area,total pore volume and average pore size of activated carbon were 2038 m2/g,2.13 cm3/g and 4.18 nm,respectively.Particularly,the mesoporous volume was 1.56 cm3/g and the mesoporous rate was 73.2%.(2)Supercapacitors are assembled using activated carbon with different pore sizes as electrode materials.The galvanostatic charge/discharge test shows that the specific capacitance of the electrode material increases with the increase of the pore size,and the mesoporous pore facilitates the migration of the electrolyte ions within the pores of the activated carbon.The shape of cyclic voltammograms of activated carbon with different pore diameter distributions is similar,that of similar rectangular shapes.In addition,there is no oxidation-reduction peak in the cyclic voltammogram of the activated carbon electrode,indicating that the activated carbon has high chemical stability.As the lesoporous rate increases,the impedance curve shows that the charge transfer resistance gradually decreases.(3)Mesoporous activated carbon loaded NiCo2O4 composite electrode materials were successfully prepared.Studies show that the NiCo2O4 nanoparticles resulted in a decrease in the specific surface area and pore volume of the composites,but the overall pore size distribution did not change much,and the mesoporous rate keep above 70%.Electrochemical tests were performed on different NiCo2O4 content of the composites.The results showed that the specific capacitance of the composite electrode material increased significantly with the increase of the content of NiCo2O4,and the specific capacitance reached the maximum at 15%.NiCo2O4 content of 15%of the composite electrode specific capacitance was up to 428 F/g,which is 66.5%higher than that of the pure mesoporous activated carbon electrode(257 F/g)But the excess NiCo2O4 nanoparticles may adhere to the pores and surfaces of activated carbon,and the specific capacitance of the composite electrode material will become smaller.In addition,the composite material is also excellent in cycle stability. |
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