Control over the morphology and phase of MnOx formed in the modified Hummers' method and impact on the electrocapacitive properties of MnOx–graphite oxide composite electrodes

Abstract

We report an one-pot method to prepare manganese oxide decorated graphite oxide as composite electrode materials for supercapacitors. Dispersed manganese oxide particles were precipitated on the graphite oxide surfaces from KMnO₄ added during the synthesis of graphite oxide by using a modified Hummers' method. The morphology and crystalline phase of the manganese oxide can be controlled by adjusting the mass ratio of KMnO₄/graphite. The sample prepared with a KMnO₄/graphite mass ratio of 2 contained nanoflowers of MnO₂ phase and exhibited a specific capacitance of 120 F g⁻¹ in 6 M KOH at a current density of 0.2 A g⁻¹. This composite retained 85% of its original capacitance after 2000 cycles, indicating an excellent stability against cycling.