Graphene nanosheets (GNs) have been successfully synthesized by one-step carbonization and simultaneous chemical activation of polyaniline (PANI) nanofibers, with large surface area (1759.5 m(2) g(-1)), high pore volume (1.16 cm(3) g(-1)) and a mesopore rich structure (volume in micropore/total ratio, 2.16%). The vital (NDs) become entrapped within a carbon lattice (to form GNs). GNs could be used as an outstanding electrode material for supercapacitors in EMIMBF4 with high cycling stability (more than 73% retention of the initial capacitance after 10,000 cycles). The symmetric supercapacitor has an excellent energy density of 170.2 Wh kg(-1) (25 degrees C) at 0.5 A g(-1), with an operating cell voltage of 4.0 V. Meanwhile, oriented activation with polymers of anisotropic geometry might be regarded as a novel process to prepare GNs. (C) 2017 Elsevier B.V. All rights reserved.