Surface microstructure modification of metal oxides also improves the electrochemical performance of metal oxide nanoparticles. The present investigation demonstrates how varying the urea molar content during the hydrothermal process altered the surfaces of MnCo2O4 nanoparticles. Successive increases of 0.1 M in urea concentration transformed the surface shape of MnCo2O4 nanoparticles from flower-like to sheet-like microstructures. Excellent electrochemical performance of MnCo2O4 nanoparticles was demonstrated in an aqueous 1 M KOH electrolyte. The improved MnCo2O4 nanoparticles have been employed to develop an asymmetric supercapacitor (ASC). The ASC device exhibits an energy density of 13 Wh/kg at a power density of 553 W/kg and a specific capacitance of 29 F g-1 at a current density of 4 mA/cm2. The MnCo2O4 nanoparticle electrode demonstrates remarkable electrocatalytic activity in both HER and OER. The MnCo2O4 electrode shows overpotential for HER and OER at 356 mV and 1.46 V, respectively. The Tafel slopes for HER and OER of the MnCo2O4 electrode are 356 mV/dec and 187 mV/dec, respectively.
Keywords: MnCo2O4 nanoparticles; TEM; asymmetric supercapacitor; hydrothermal; supercapacitor.