▎ 摘　　要

Benefitting from its unique characteristics, graphene has been considered as one of promising electrode material candidates for supercapacitors. Nevertheless, the accessible specific surface area for the charge storage in electrodes and the solvated ion transport in electrolyte are seriously deteriorated in the conventional graphene, leading to the poor rate capability and low specific capacitance. Thus, it is urgent to construct a hierarchical porous structure with suitable surface area for graphene to enhance its capacitive performance. In this work, a facile freeze drying-calcination strategy is adopted to fabricate hierarchical porous reduced graphene oxide (p-rGO) by using Fe(NO3)(3) as activator. The etching effect is optimized by adjusting the dosage of Fe(NO3)(3) applied. Compared with the pristine rGO, the resultant p-rGO delivers better capacitive performance, whose specific capacitance reaches 210.1 F g(-1) at 1 A g(-1) in the three-electrode system with 6.0 M KOH solution as electrolyte. Moreover, the p-rGO-3 based symmetric supercapacitor possesses an energy density of 21.54 Wh kg(-1) at a power density of 160.42 W kg(-1), and exhibits superior electrochemical stability even after 10,000 charge-discharge cycles. The enhanced capacitive performance is presumably contributed by the hierarchical porous architecture and the doping of nitrogen.