fig8

Figure 8. Electrochemical performances of the assembled symmetric supercapacitor by ONPC-900//ONPC-900 in a two-electrode system. (A) CV curves and (B) GCD curves at a scan rate of 100 mV s^-1 with various current potential windows, respectively; (C) CV curves were measured at various scan rates (5-500 mV s^-1); (D) GCD profiles were measured at different current densities (0.5-20 A g^-1); (E) SC; (F) Ragone plots, and (G) Cycle life and Coulombic efficiency testing after 30,000 cycles at 5 A g^-1 in 6.0 mol L^-1 KOH, inset are the enlarged impedance profile before and after a cyclic stability test. ONPC: O, N co-doped hierarchical porous carbon; CV: Cyclic voltammetry; GCD: Galvanostatic charge-discharge; SC: Specific capacitance.