Preparation And Electrochemical Properties Study Of Activated Carbon Fibers

Activated carbon fiber is a new type of adsorbent material with different physical and chemical properties from traditional granular and powdered activated carbon materials.It is rich in pore structure,surface activity and adsorption performance.It is widely used in sewage treatment,gas separation,medical treatment and electronic military and other fields.Meta-aramid as a new type of organic polymer,its high crystallinity,good heat resistance,good chemical stability,is the ideal precursor for the preparation of activated carbon fiber.In this paper,activated carbon fibers were prepared by physical and chemical activation methods using polymer waste as precursors and used as electrode materials for electric double layer capacitors.The effects of activator type and dosage,activation temperature and activation time on the adsorption properties of activated carbon fiber were investigated.Secondly,the effects of different activation methods on pore structure and chemical properties were analyzed by means of nitrogen adsorption,infrared spectroscopy and XPS.The different mechanism of activation methods were also discussed.Finally,the effects of specific surface area,pore size distribution and chemical properties on electrochemical properties of the activated carbon fibers were investigated.The results show:(1)The activated carbon fibers with high specific surface area can be prepared by physical and chemical activation methods,Increasing activation temperature,prolonging activation time and increasing amount of activator can enhance adsorption performance of activated carbon fiber and improve its specific surface area.The specific surface area of the ACFs by CO2,H3PO4 and KOH activation were as high as 2000m2/g,1700m2/g and 3300m2/g respectively.(2)The pore structure and surface chemical properties of activated carbon fibers prepared by different activation methods are different.The pore size of ACFs obtained by H3PO4 activation is the smallest,and the pore size of ACFs by CO2 activation is larger,the pore size of ACFs by KOH activation is the largest.In addition,the increase of phosphoric acid concentration increases the content of nitrogen,oxygen and phosphorus atoms on the surface of activated carbon fibers,while the increase of potassium hydroxide content reduces the content of surface nitrogen and oxygen atoms.(3)The electrochemical properties were effected by specific surface area,pore size distribution and surface chemical properties of the activated carbon fibers.In general,the specific capacitance is proportional to the specific surface area.Secondly,the presence of moderate pore is beneficial to the improvement of electrochemical performance.In addition,nitrogen,oxygen,phosphorus elements help to improve the hydrophilicity of the electrode material,thus optimizing the electrochemical performance.