Effect of Ag-Doping on the Capacitive Behavior of Amorphous Manganese Dioxide Electrodes

Amorphous MnO2 and Ag-doped MnO2 thin films were galvanostatically deposited on a polished stainless steel substrate from 20 mM KMnO4 aqueous solutions without and with AgNO3 additions at cathodic current density of 1 mA/cm2 for the application in electrodes of electrochemical supercapacitors. The supercapacitive properties of the deposited thin films have been studied in 0.5 M Na2SO4 electrolyte by cyclic voltammetry, impedance spectroscopy, and charge-discharge measurement techniques. The Ag-free MnO2 film showed better capacitive behavior and lower charge transfer resistance compared to the Ag-doped MnO2 films. The specific capacitance and charge transfer resistance values for Ag-free MnO2 films were 160 F/g at a scan rate 10 mV/s and 3.87 Ω, respectively. Cyclic stability using charge-discharge measurement technique indicates the excellent stability of Ag-free MnO2 films and its possible use as a low cost electrode for supercapacitor applications.