Synergistic MnO2/Co3O4 composites for enhanced asymmetric supercapacitor and electrocatalytic applications

This study reports MnO 2 /Co 3 O 4 composites synthesized via hydrothermal route and employed for energy storage and water splitting applications. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis shows the crystalline nature with rods (MnO 2 ), nanosphere (Co 3 O 4 ) and nanoflowers (MnO 2 /Co 3 O 4 ) like morphologies. The specific capacitance ( C s ) of MnO 2 , Co 3 O 4, MC-(0.7:0.3), MC-(0.5:0.5) was calculated from cyclic voltammetry (CV), at 5 mV/s are 32.4, 40.44, 85.41, 121.32 F / g and from the galvanometric charge discharge (GCD), at 1 A/g, as 38.33, 46.6, 91.6, 133.4 F/g respectively. The enhanced C s of the composite electrode is attributed due to the high surface area and the electrical conductivity of Co 3 O 4 . EIS analysis shows MC-(0.5:0.5) electrode have lowest solution resistance ( R s ) of 1.15 Ω and charge transfer resistance ( R ct ) of 40 Ω. The LSV polarization curves shows the composites have low overpotential of 245 mV (MC-(0.5:0.5)) and 220 mV (MC-(0.7:0.3)) at the current density ( I d ) of 10 mA/cm 2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities respectively as compare to MnO 2 and Co 3 O 4 . These results demonstrated that the composite electrodes exhibited high electrochemical and electrocatalytic performances as compare to MnO 2 and Co 3 O 4 for both supercapacitor and electrocatalytic water splitting applications.