Supercapacitive Behaviors of Hierarchically Porous Carbons Prepared by Metal Oxide/Surfactant Templates

Abstract

The hierarchically porous carbons (HPCs) have been prepared by sol-gel self-assembly process with nickel oxide and surfactant as the dual template. The as-prepared HPCs are further activated by HNO3. The specific surface area and pore structure of the activated HPCs are characterized by nitrogen adsorption–desorption isotherm at 77 K, Field emission scanning electron microscope (FE-SEM), and Field emission transmission electron microscope (FE-TEM). Furthermore, the electrochemical performances of the activated HPCs are studied by cyclic voltammetry, galvanostatic charge-discharge, cycle life and electrochemical impedance spectroscopy (EIS) in 6 M KOH. The results indicate that the activated HPCs demonstrate special pore structures, i.e., a lot of mesopores distributed on the wall of the macropores providing not only high specific surface area but also transport path of electrolyte ions. The total pore volume of activated HPCs is 0.61 cm3 g−1, and the average pore diameter is 1.02 nm. Due to the unique microstructure and the high specific surface area, the activated HPCs show excellent supercapacitive behavior. The maximum specific capacitance obtained from cyclic voltammetry is about 272 F g−1 at a scan rate of 1 mV s−1. Moreover, the maximum energy density and maximum the power density are about 8.3 Wh kg−1 and 17.5 kW kg−1, respectively.