Fig. 5

The CV curves under different scan rates of 5, 10, 20, 40, 50, and 100 mV s⁻¹ of samples a CMO-1, b CMO-4, c CMO-8, d CMO-12, and e CMO-24 in the potential window ranged from − 0.2 to + 0.6 V. f The specific capacitance of samples under different scan rates of 5–100 mV s⁻¹. The inset in f is the plots of anodic and cathodic peak current against the square root of the scan rate