fig5

Figure 5. Electrochemical properties of ONPC materials in a three-electrode configuration. (A) CV plots of ONPC-900 measured at various scans (5~500 mV s^-1); (B) GCD curves of ONPC-900 measured at various current densities; (C) GCD profiles of ONPC materials; (D) CV curves of ONPC materials; (E) SC comparison of ONPC materials measured at different current densities; (F) Nyquist plots of ONPC materials, inside is the zoomed high-frequency region of ONPC materials; (G) Comparison of the SC with these reported coal-derived carbon materials or ONPC materials^[41,44-61]; (H) Radar chart for comparison of seventeen structural and test features and SC (F g^-1) of all ONPC materials based on experiment in this work. In particular, the high grades in D_ave (average pore diameter) mean low values. ONPC: O, N co-doped hierarchical porous carbon; CV: Cyclic voltammetry; GCD: Galvanostatic charge-discharge.