Figure 4.

CV curves of MnO₂ and GQDs/MnO₂‐3 at a scan rate of 20 mV s⁻¹. b) CV curves of GQDs/MnO₂‐3 at different scan rates (5–100 mV s⁻¹). c) Specific capacitances of all samples as a function of the scan rate. d) GCD curves of all samples at current of 1 mA. e) Nyquist plots in a frequency range from 0.01 Hz to 100 kHz for all samples. f) Cycling stability tests over 10 000 cycles for MnO₂, GQDs/MnO₂‐3, and GQDs/MnO₂‐10.