MnO2 hierarchical microspheres assembled from porous nanoplates for high-performance supercapacitors

Abstract

Novel three-dimensional (3D) MnO2 hierarchical microspheres (HMSs) assembled by porous nanoplates with a thickness of 50–130 nm were solvothermally prepared and combined with subsequent annealing of the precursors at 450 °C in air. Such MnO2 HMSs possessed a BET specific surface area of 48.6 m2 g−1 with a mean pore size of about 14.5 nm, respectively. The shapes and size of final MnO2 products can be controlled by changing the amount of surfactant cetyltrimethylammonium bromide (CTAB) and volume ratios of water to ethanol. Irregular particles were produced in the absence of water, and the morphologies of MnO2 samples transformed from well-defined HMSs to microcubes with the content of water increasing. These MnO2 HMSs show both a high specific capacitance of 129 F g−1 at 0.5 A g−1 in 0.5 M of Na2SO4 aqueous solution and a good cycling stability of 98.6% capacitance retention after 1000 cycles at a current density of 1 A g−1, demonstrating very excellent electrochemical performance. The result suggests that such MnO2 HMSs may be a promising electrode material in the field of supercapacitors due to its mesoporous and integrated hierarchical structure.