In order to control the amount of manganese oxide coated onto a graphite surface, immersion durations were varied. A maximum capacitance of 490 mF cm−2 was obtained in 0.5 M NaCl and using an immersion time of 20 min and a current of 1 mA. In addition, for the manganese oxide electrode, the lower the current, the higher the capacitance and the higher the immersion time, the higher the resistance. Furthermore, the chronopotentiometric (CP) charge–discharge curves were symmetrical and featured similar isosceles triangles, which demonstrate high electrochemical reversibility and good stability. Cyclic voltammograms of the manganese oxide electrode demonstrate that its operational stability is high.
