The effects of surfactant template concentration on the supercapacitive behaviors of hierarchically porous carbons

The hierarchically porous carbons (HPCs) are prepared by sol–gel self-assembly technology at various surfactant concentrations (from 0 to 0.55 mol L−1). The influences of the surfactant (CTAB) concentration on the physical and electrochemical properties of the activated HPCs are investigated by nitrogen adsorption–desorption isotherm, cyclic voltammetry, galvanostatic charge–discharge, cycle life, electrochemical impedance spectroscopy (EIS) and self-discharging in 6 M KOH electrolyte. The results demonstrate that the concentration of surfactant template is a crucial factor impacting the characteristics of HPCs. With the change of surfactant concentration, the activated HPCs at CCTAB = 0.27 mol L−1 (HPCs-3) shows the largest specific surface area of 689 m2 g−1. In addition, the activated HPCs show excellent supercapacitive behaviors and three sections self-discharge mechanism. Especially, the activated HPCs-3 appears superior electrochemical stability, low IR drop of 0.01 V, and the maximum specific capacitance of 272 F g−1 obtained from cyclic voltammetry at the scan rate of 1 mV s−1. Moreover, the supercapacitor used the activated HPCs-3 as electrode active material exhibits a specific capacitance of 61 F g−1 at the current density of 1 A g−1, and keeps a specific capacitance of 60 F g−1 after 5000 consecutive charge/discharge cycles.

► Hierarchically porous carbons with micro–meso–macro structures prepared by templates.
► Template concentration obviously affects the physical and electrochemical properties.
► Three sections mechanism exists in self-discharge process.