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

Abstract

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.