Influence of electrodeposition modes on the electrochemical performance of MnO2 films prepared using anionic MnO4− (Mn7+) precursor

Abstract

In this work, we report the comparative electrochemical performance of the nanostructured MnO2 films prepared via three different electrodeposition modes, namely, potentiostatic (PS), potentiodynamic (PD), and galvanostatic (GS), using anionic MnO4- (Mn7+) precursor. All the MnO2 films have been found to exhibit the hexagonal crystallographic phase of epsilon manganese dioxide (ε-MnO2, akhtenkite), consistent with the JCPDS card no. 12-0141. The potentiostatically electrodeposited MnO2 film has surface morphology exhibiting a porous microstructure comprising of sparsely distributed grains, which is conducive for easy diffusion of electrolyte ions during electrochemical process. The analyses of atomic force microscopy images reveal that the surface area is maximum for the film deposited via PS mode. Cyclic voltammetry studies reveal that the film deposited via PS mode has the maximum specific capacitance 259.4F/g, followed by 187.1F/g and 180.3F/g for the films deposited via PD and GS modes, respectively at the scan rate of 5mV/s. The galvanostatic charge/discharge measurements at the current density of 1mA/cm2 show the specific capacitance to be maximum 325.6F/g for the MnO2 film prepared via PS mode, followed by 194.6F/g and 182.5F/g for the films prepared by PD and GS modes, respectively. The variation in specific capacitances of the films is attributed to varying morphological features of the films. In conclusion, the PS mode has been found to be the optimum electrodeposition mode to prepare MnO2 films using anionic MnO4− (Mn7+) precursor for improved electrochemical performance of the films.