Facile synthesis of hierarchical hollow ε-MnO2 spheres and their application in supercapacitor electrodes

The hierarchical hollow microspheres of e-MnO{sub 2} have been synthesized through a facile chemical method at room temperature followed by selective removal of manganese carbonate structures with HCl. The microstructure and morphologies of the resulting materials are investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results indicate that the product obtained by simple reaction for 3 min has a porous shell with excellent permeability and uniform pore-size distribution. Electrochemical properties were characterized by cyclic voltammetry, galvanostatic charge/discharge and impedance spectra. As a result, the hierarchical hollow e-MnO{sub 2} showed the specific capacitance of 115 F g{sup −1} at 0.5 A g{sup −1}. These results demonstrate that the e-MnO{sub 2} as electrode materials have potential application for high-performance supercapacitors. - Graphical abstract: The MnO{sub 2} shell with MnCO{sub 3} intermediate core is prepared at room temperature; the hollow structure with excellent permeated shell enhanced the discharge capacity and electrochemical stability.