Concentration dependent structure evolution and electrical properties of MnO2 nanostructures

• Nanostructured MnO2 were synthesized by a template-free hydrothermal route.
• The transition from MnO2 nanospheres to MnO2 nanowires was observed.
• The specific capacitance of MnO2 nanowires is 1.8 times that of MnO2 nanospheres.

MnO2 with various nanostructures was prepared by a facile hydrothermal method. X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) together recorded the composition and structure evolution during the entire produce process by adjusting the amount-of-substance concentration of precursors. It was found that the wormlike MnO2 nanospheres evolved toward nanowires along with the increasing of the concentration. Such MnO2 nanowire showed a high specific capacitance of 405 F g−1 at 2 mV s−1 and an attractive cycling stability of 99.0% retention after 1000 cycles. The method presented in this paper also gives us new inspires to improve the electrochemical properties of other nanostructured materials.