A Novel Asymmetric Supercapacitor Designed with Mn3O4@Multi-wall Carbon Nanotube Nanocomposite 
and Reduced Graphene Oxide Electrodes
We demonstrate a straightforward process for the synthesis and fabrication of a hybrid-type asymmetric supercapacitor (ASC) by combining Mn3O4 nanoparticle-supported multi-wall carbon nanotube (Mn3O4@MWCNT) composite as positive and reduced graphene oxide (rGO) as negative electrodes. A controlled hydrothermal synthesis of Mn3O4 in the presence of MWCNT resulted in a well-distributed Mn3O4 nanoparticles on the MWCNT backbone in the Mn3O4@MWCNT composite. The structure and morphology of the as-prepared materials have been investigated by x-ray diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller analysis and x-ray photoelectron spectroscopy measurements. The electrochemical characterizations were carried out in terms of cyclic voltammetry, galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy analysis. The constructed ASC with 1 M KOH-supporting electrolyte was able to provide high-specificity capacitance of 173.36 F/g at 2 mV/s scan rate and high-energy density of 26.8 Wh/kg accompanied by high cycle stability with 79.3% capacitance retention over 3000 GCD cycles.