Fig. 4From: Enhanced Capacitive Performance of N-Doped Activated Carbon from Petroleum Coke by Combining Ammoxidation with KOH Activation a CV curves at a scan rate of 10 mV s−1. b GCD curves at a current density of 5 A g−1. c Specific capacitance at various current densities from 1 to 20 A g−1. d Nyquist plots. The inset is the magnified Nyquist plots at the high-frequency regionBack to article page