V to 0 V at 1 Ag -1 , which displayed triangular shapes indicating good reversible performance of the fabricated electrodes in charge and discharge process. Among three fabricated electrodes, PC-750 exhibited highest specific capacitance of 274.9 F g -1 with a capacity retention of 73.2%, and the coulombic efficiency of 98.9% after 1000 cycles which further verified its outstanding rate capability and cycling stability. From the GCD analysis, the specific capacitance of a symmetric two-electrode system was found to be 102.1 F g -1 at 1 A g -1 . The electrode exhibited the highest specific capacitance of 147.7 F g -1 at 1 A g -1 current density, with a retained capacity retention rate of 75.8% from 1 A g -1 to 12 A g -1 current density.