Preparation And Performance Of Activated Carbon For Supercapacitors Derived From Rice Husk

Supercapacitors,a new type of energy storage device,are currently drawing growing attention owing to their high power density,long cycle life and ultra-fast charge rate,which are desirable for applying to many fields.However,low energy density and high production cost have limited the large scale application of supercapacitors.The electrochemical performance of supercapacitors is deeply affected by electrode materials.Therefore,it is significant to optimize the structure of electrode materials.In this paper,the agricultural waste rice husk was taken as the raw material to synthesize the activated carbon by activating pyrolytic char and hydrothermal char with using KOH activator.In addition,both the properties of pyrolytic char and hydrothermal char,and the activation conditions had influenced on the electrochemical performance of the activated carbon,which were also discussed.The results indicated that the activated carbon derived from rice husk showed excellent electrochemical performance.The study found that the specific surface area and specific capacitance of the activated carbon produced from activating pyrolytic char changed with different activation times,activation temperatures and activator ratios,on which the effects of the activator ratio was most significant therein.The activated carbon exhibited the highest specific surface area of3464 m~2/g.And in 6 M KOH electrolyte,using a standard two-electrode system,the specific capacitance of the material(at 2h,3:1,800?)achieved 300 F/g at 0.2A/g and it retained capacity of 82.8%after 10000 cycles.The activated carbon as electrode materials showed good rate performance and cycle stability.Porous carbon materials were prepared by activating pyrolytic char and hydrothermal char at different activator ratios.Both the physical characterization and the electrochemical performance of carbon materials were studied and compared.According to the comparison,pyrolytic char and hydrothermal char differed in elemental composition and content of components,and the differences also made a great impact on the structure and specific capacitance of activated carbon materials.Besides,the results of electrochemical measurements showed that the hydrothermal char-based activated carbon possessed better electrochemical properties.The porous carbon produced from hydrothermal char and made at the ratio of 3:1 had the specific surface area of 3297 m~2/g,and exhibited outstanding electrochemical performance(353 F/g at 0.2A/g)in 6 M KOH electrolyte.Moreover,such porous carbon realized a high energy density of 12.26Wh/kg and maintained 84.1%specific capacitance after 10000 cycles.