Effect of aqueous electrolytes on the electrochemical behaviors of supercapacitors based on hierarchically porous carbons

Hierarchically porous carbons (HPCs) have been prepared by sal-gel self-assembly technology with nickel oxide and surfactant as the dual template. The porous carbons are further activated by nitric acid. The electrochemical behaviors of supercapacitors using HPCs as electrode material in different aqueous electrolytes, e.g., (NH4)(2)SO4, Na2SO4, H2SO4 and KOH are studied by cyclic voltametry, galvanostatic charge/discharge, cyclic life, leakage current, self-discharge and electrochemical impedance spectroscopy. The results demonstrate that the supercapacitors in various electrolytes perform definitely capacitive behaviors; especially in 6 M KOH electrolyte the supercapacitor represents the best electrochemical performance, the shortest relaxation time, and nearly ideal polarisability. The energy density of 8.42 Wh kg(-1) and power density of 17.22 kW kg(-1) are obtained at the operated voltage window of 1.0 V. Especially, the energy density of 11.54 Wh kg(-1) and power density of 10.58 kW kg(-1) can be achieved when the voltage is up to 1.2 V. (c) 2012 Elsevier B.V. All rights reserved.