Shape-controlled synthesis of hierarchical hollow urchin-shape α-MnO2 nanostructures and their electrochemical properties

• α-MnO2 nanotubes-assembled hollow urchins have been prepared.
• HCl plays the crucial role in the formation of the nanotubular structure.
• The unique MnO2 superstructure shows better electrochemical performance.

3D hierarchical hollow urchin-shape α-MnO2 nanostructures have been synthesized using a simple one-step hydrothermal process in an acidic KMnO4 solution without employing any templates or surfactants. The structure and morphology of the products were characterized by XRD, FTIR, SEM and TEM. The hierarchical hollow urchins were found to be assembled from single crystalline α-MnO2 nanotubes. The formation mechanism of the unique superstructure was investigated systemically by varying the synthesis conditions. Electrochemical studies indicated that these α-MnO2 nanotubes-assembled hollow urchins exhibited favorable performance compared to the α-MnO2 nanorods-assembled microspheres as electrode materials in supercapacitor. Due to the distinct architecture of macroporous hollow structure and nanotubular building blocks, the sample delivered a specific capacitance of 123 F g−1 with superior rate capability.