Electrochemical supercapacitor studies of porous MnO2 nanoparticles in neutral electrolytes

In this study, porous MnO2 nanoparticles (sample A and sample B) with higher active surface area were synthesized using sonochemical and soft template methods. To determine the crystalline phase, the samples were characterized to study their microstructure, chemical composition, and physical properties. X-ray diffraction results showed that both the samples were amorphous. Microstructure study confirmed that the sample A is spherical, existing with rod-shaped morphology whereas sample B shows flake-like morphology. The Brunauer-Emmett-Teller results showed the value obtained for sample B to be 1559 m2 g−1, which is effectively high when compared to that of sample A. The electrochemical capacitor behavior of the prepared nanoparticles was investigated in 0.1 M Li2SO4 and Na2SO4 electrolytes. The cyclic voltammogram result showed that both the sample electrodes behave as an ideal capacitor in both electrolytes. The charge-discharge test result indicated that the highest specific capacitance value of 280 F g−1 was obtained for sample B electrode in Na2SO4 electrolyte with good capacity retention of 92.31% after 500 cycles. The electrochemical impedance spectroscopy measurements confirm that sample B electrode has a lower Rct value in Na2SO4 electrolyte when compared to that in Li2SO4 electrolyte.