Double-shelled MnO2 hollow spheres for supercapacitors

Double-shelled MnO2 hollow spheres were prepared through a self-template route, by the double oxidation-dissolution rounds of the MnCO3 precursors. X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), field emission scanning microscopy (FESEM) and transmission electron microscopy (TEM) together record the composition and structure evolution during the entire process. The multilayer hollow spheres contain a central hollow interior and a clear gap between the outer and inner shells. Such hollow MnO2 nanoparticles have great potential in energy storage and conversion, showing a high specific capacitance of 210.2 F g(-1) at 0.2 A g(-1) and an attractive capacity retention ratio of 86.2% when current density increases 25 times to 5 A g(-1). (C)2014 Elsevier B.V. All rights reserved.