Controllable synthesis and characterization of α-MnO₂ nanowires

Size controllable α-MnO₂ nanowires were synthesized from KMnO₄ and ethanol via a low-temperature hydrothermal route assisted with subsequently heat treatment. No acid or alkali was added. XRD and SEM results clarified α-MnO₂ nanoparticles (5-30 nm) began to form at room temperature, and then grew up to nanowires (~12 nm in diameter) when temperature increasing up to 120-160 °C for an appropriate reaction time. Otherwise, octahedron-like Mn₃O₄ began to form at 120 °C more than 4 h or at 160 °C more than 2 h. Hydrothermal-synthesized α-MnO₂ show well thermal-stability even it was heated at 900 °C. And various size α-MnO₂ nanowires were controllable prepared by adjusting heat treatment temperature of hydrothermal-synthesized α-MnO₂ at range from 150 °C to 750 °C for 3 h, which show the strongest diffraction peak (211) plane. The capacity of hydrothermal-synthesized α-MnO₂ at 120 °C for 2 h was about 125 F/g, which exhibited a promising electrochemical property.