Preparation and pseudo-capacitance of birnessite-type MnO2 nanostructures via microwave-assisted emulsion method

A microwave-assisted emulsion process has been developed to synthesize birnessite-type MnO2 one-dimensional (1D) nanostructures. The prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). TEM images confirmed that the particles were composed of nanowires and nanobelts. As a consequence of the small size, such MnO2 nanostructures exhibit a high specific capacitance of 277 F g−1 at the current density of 0.2 mA cm−2. Furthermore, the simple synthetic approach may provide a convenient route for the preparation of birnessite-type MnO2 nanowires and other 1D nanostructured materials on a large scale.