Effect of morphology of manganese oxide on the capacitive behavior of electrodes

Manganese oxide (MnO₂) was synthesized by reduction of potassium permanganate followed by calcination in air at 200, 400 and 600 °C. Morphology and structure of MnO₂ was characterized by scanning electron microscopy and X-ray diffraction, respectively. Electrochemical characterization of MnO₂-based electrodes was carried out by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). CV results revealed that MnO₂-based electrode calcined at 200 °C showed maximum specific capacitance of 177 F g^-1 at a scan rate of 1 mVs^-1 in 3 M potassium hydroxide. EIS analysis of electrode produced with MnO₂ that was calcined at 200 °C showed solution resistance and charge transfer resistance values of 0.421 and 1.605 Ω, respectively. CV results also revealed that MnO₂-based electrodes showed capacitance retention of 89 % at 50 mVs^-1 scan rate for 1000 cycles.