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.