Microwave-assisted rapid synthesis of birnessite-type MnO2 nanoparticles for high performance supercapacitor applications

Birnessite-type MnO2 nanoparticles have been successfully synthesized by the microwave-assisted reflux as short as 5 min. The microstructure and morphology of the products were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, scanning electron microscopy, transmission electron microscopy. The electrochemical properties of the as-prepared MnO2 as an electrode material for supercapacitor were investigated by cyclic voltammetry and galvanostatic charge-discharge measurements in 1 M Na2SO4 electrolyte, and a high specific capacitance of 329 F g−1 was achieved at a current density of 0.2 A g−1. The specific capacitance retention was 92% after 1000 cycles at 2 A g−1, suggesting that it is a promising electrode material for supercapacitors.