Preparation And Electrochemical Stability Of Heteroatom Doped Activated Carbons

Activated carbon is the most widely used electrode material for supercapacitors,it is usually considered that the hetero atomic dopant can enhance the specific capacity of activated carbon electrode.However,how heteroatoms doping infulence the preparation of activated carbons has rarely been reported,and it is seldom known the research how hetero atoms influence the electrode stability of ultracapacitor.Therefore,the effect of sulfur and nitrogen doping on the activation reaction of asphalt based petroleum coke was investigated,it found that the quality loss rate of sulfur/nitrogen doped petroleum coke?SNC?after activation is higher than that of undoped petroleum coke?C?,and the specific surface area of sulfur/nitrogen-dped active petroleum coke?ASNC?is higher than that of undoped active petroleum coke?AC?,which indicates that sulfur and nitrogen doping can improve the activation activity of petroleum coke.In addition,we explored the activation law of KOH,CO₂,NH₃ and water vapor activating,it found that increaing the amount of NH₃ had no effect on the activation,but the activation effect would be enhanced after increasing the amount of KOH or CO₂.When the activation time of KOH or NH₃ was extended,the activation effect does not change,on the contrary CO₂ or water vapor activationwould be enhanced.When the activation temperature was increased,the activation effect of NH₃ was basically unchanged,while the activation effect of KOH,CO₂ and steam activation were strengthened.By XPS analysis,it manifested the nitrogen content of SNC reduced after the activation using CO₂,which showed that nitrogen can improve the activation activity of SNC;then,the sulfur content of SNC decreased after the activation using NH₃,it indicated sulfur can enhance the activation activity of SNC;finally,sulfur and nitrogen of SNC were damaged after water vapor activation.We also studied how sulfur and nitrogen doping influenced the electrochemical stability of starch based porous carbon electrode in supercapacitor,it found that sulfur-doping porous carbon electrode in the symmetric supercapacitor had a higher electrochemical activity,which leaded to a poor stability,it is also found that the charging voltage was difficult to reach the cut-off voltage in the program of galvanostatic charge-discharge when the electrode in asymmetric capacitor was activated carbon,especially at a current density of 0.25 A/g,which even leaded to electrolyte decomposition.