▎ 摘　　要

Supercapacitor, as a new energy storage system, has attracted increasing interests owing to its fast charge/discharge process, high-power density, and long-cycling life. However, exploring high-capacitance porous carbons as electrode materials has caused enormous attention around the world. Herein, we propose a nitrogen-doped porous carbon (NPC)-sandwiched 3D graphene (NPC-3DG) by direct freeze-drying of ZIF-8/graphene oxide mixed solution followed by a high-temperature thermal treatment. The characterizations of scanning electron microscopy, N-2 adsorption/desorption isotherms, and X-ray photoelectron spectroscopy proves the sandwich structured frameworks of NPC-3DG with a high specific surface area of 726.9 m(2) g(-1) and a nitrogen content of 3.2 wt%. When used as capacitive electrode materials (in three-electrode system), the resultant NPC-3DG exhibited a high capacitance of 530.1 F g(-1) at a current density of 1 A g(-1). Moreover, the capacitance still maintains a high value of 337.2 F g(-1) even at a high current density of 20 A g(-1).