KCl/MgO Composite Templates for Achieving Hierarchical Porous Carbons with High Performance in Supercapacitor

Abstract Simple and convenient protocols for fabricating hierarchical porous carbons (HPCs) are highly imperative owing to their superior electrochemical performance. This work prepared a kind of KCl/MgO composite templates for synthesizing HPCs from polyethylene glycol‐200 carbon precursor with one‐step pyrolysis. The results show that the ratio of KCl and MgO can profoundly influence the morphology and microstructure of HPCs. At 50 wt % of KCl, the HPC‐5 displays the largest specific surface area and contains the best pore‐size distribution. When used as the supercapacitor electrodes without conductive additives, the HPC‐5 has a maximum capacitance (321.82 F g −1 at 0.5 A g −1 ), excellent rate performance (68.9 % of capacitance retention at the high current density of 10 A g −1 ), as well as remarkable cyclic stability (98 % capacitance retention after 5000 cycles) in aqueous electrolyte of 6 M KOH. When assembled into a symmetrical double‐electrode system, the HPC‐5 provides a high energy density of 11.20 Wh kg −1 at 390.66 W kg −1 power density in 1 M Na 2 SO 4 . The composite template methods are proposed as a promising route for the controllable synthesis of HPCs with high electrochemical properties.