Morphological Transformations and Electrochemical Properties of Hydrothermally Synthesized MnO_2 Nanostructures

摘要

MnO_2 nanostructures with various morphologies were synthesized by the hydrothermal method with control over the reaction temperature and dwell time. One dimensional (1D) nanoneedle structure can self-assemble to form three dimensional (3D) microspheres of MnO_2 nanoneedles at 95°C by extending the dwell time from 3 hours to 15 hours. Alternatively, the 3D microspheres of nanoneedles can transform into 1D nanobelts and nanorods by increasing the reaction temperature to 120°C and 165°C, respectively, while maintaining constant dwell time of 15 hours. The supercapacitance of these nanostructures shows strong morphology dependence, and nanobelts have the highest specific capacitance of 323.7 F g~(-1).