▎ 摘　　要

Polyacrylonitrile nanofiber cloth coated with graphene oxide was carbonized and activated to fabricate nitrogen- and oxygen-enriched porous carbon/graphene (NAC@Gr) sandwich-like composites. The influence of graphene coating on the microstructure, surface composition, and supercapacitive performance of the as-prepared composites was investigated. The results indicated that significantly enhanced energy storage capability can be achieved due to the high specific surface area, optimized pore structure, and surface functionality. The composites show both high gravimetric and volumetric specific capacitances, for example, 380 F g(-1) (178 F cm(-3)) at 0.1 A g(-1) in 6 M KOH and 228 F g(-1) (125 F cm(-3)) at 1 A g(-1) in 1 M TEABF(4)/AN electrolyte. The assembled symmetric supercapacitors exhibit high energy density, high power density, excellent cycling stability, and high-rate performance.