Sodium-Ion-Assisted Hydrothermal Synthesis of γ-MnO[sub 2] and Its Electrochemical Performance

A nanomaterial was synthesized by hydrothermally treating an amorphous manganese oxide, which was obtained by the reaction between and at ambient conditions. It is only in a narrow range of adding an amount of NaOH (e.g., in our case) that can be obtained. The addition of NaOH may affect the radii of hydrated and, consequently, the formation of ; the related mechanism was discussed. was characterized by X-ray diffraction (XRD), scanning electron microscope, transmission electron microscope, and temperature-programmed XRD. was also characterized by the combined thermogravimetric/differential thermal analysis–mass spectrometry; accordingly, the annealed forms of were prepared and characterized electrochemically. The results show that the calcined at for showed excellent capacity with a good rate capability.