Solution-combustion synthesis of ε-MnO2 for supercapacitors

ε-MnO2 nanoparticles were synthesized through a single step solution combustion process without using any template or surfactants. Plate-like ε-MnO2 materials, 50–150 nm in diameter and 20–25 nm in thickness, were obtained at a higher Mn(NO3)2:C2H5NO2 molar ratio (i.e., 2:1), whereas spherical ε-MnO2 particles (about 60 nm in diameter) were obtained as the Mn(NO3)2:C2H5NO2 ratio is lower (e.g., 1:2). Electrochemical performance of the as-prepared ε-MnO2 nanoparticles was examined. The spherical ε-MnO2 nanoparticle sample shows a relatively higher specific capacitance of 123 F g− 1 at the current density of 1 A g− 1 in 1 M NaSO4 electrolyte solution, probably due to its porous structures and higher surface areas in comparison with the plate-like counterparties.