Hydrothermal synthesis of manganese oxide (Mn3O4) with granule-like morphology for supercapacitor application

In the present work, we have synthesized manganese oxide (Mn3O4) nanoparticles (NPs) using the facile hydrothermal route at different pH (9, 10. 11). The effect of the pH variation on the structural and electrochemical properties of the synthesized Mn3O4 NPs have studied. Synthesized NPs are characterized using XRD, SEM, EDS, TEM, BET, cyclic voltammetry, galvanic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) for various properties. The preferred orientation of Mn3O4 growth is along the (211) plane with granule-like morphology. The Mn3O4 electrodes were fabricated and investigated for electrochemical characterizations. The capacitance of the Mn3O4 electrode was calculated from cyclic voltammetry (CV) and galvanometric charge-discharge curves at different scan rates and current densities, respectively. The specific capacitance values of the Mn3O4 electrode (pH 11) were estimated from CV and GCD viz 277 F/g and 262 F/g, respectively, with the higher capacitance retention. Charge transfer resistance was calculated from electrochemical impedance spectroscopy (EIS) measurements. The equivalent series resistance for Mn3O4 at pH 11 is around 0.015 Ω. Nanostructured MnO2 electrodes can be the potential materials for supercapacitor application.