Facile hydrothermal synthesis of one-dimensional nanostructured α-MnO2 for supercapacitors

• The nanowires and nanorods of α-MnO2 possessed uniform microstructure, good crystallization and well structural stability.
• The wire-like MnO2 exhibited better electrochemical reversibility and capacity than that of the rod-like one.
• The wire-like and rod-like α-MnO2 presented fine cycle stability after continuous charge–discharge cycles.

α-MnO2 recently becomes a promising candidate of electrode materials for high effective supercapacitors in which it possesses of unique structure of 2×2 tunnels that can provide more electrons and ions diffusion paths. In this work, different morphologies MnO2 with α-phase crystalline structure have been prepared via a one-step facile hydrothermal method by adding various reagents. Compositions, microstructures and morphologies of these as-synthesized materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and electrochemical properties of α-MnO2 electrodes were studied by the cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) in 1 M Na2SO4 aqueous solution. The specific capacitance of nanowires were 158 F g−1 while the specific capacitance of nanorods were 106 F g−1 at current density of 4 A g−1, and improved performance of the wire-like electrode material was probably ascribed to the larger specific surface area that can provide relatively more active sites for high capacity. Meanwhile, both the nanowires and nanorods of MnO2 presented fine cycle stability after continuous multiple charge/discharge times.