▎ 摘　　要

Supercapacitors are attractive, in comparison with batteries, for their high power density, instant chargeability, and long cycle life. Manganese oxide (MnOx) can theoretically store charges up to 1300 F/g in aqueous electrolytes but usually suffers from low electrical conductivity resulting in low capacitance values. Anchoring nano-MnOx on conductive high-surface graphene will improve the charge storage performances. In this study, we fabricate three different kinds of graphene/manganese oxide nanocomposites made up of nanoparticle Mn3O4, nano-particle MnO2, or nanorod-petal MnO2 anchored on reduced graphene nanosheets (RG) or nitrogen-doped RG (NRG). These materials are systematically characterized with field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The capacitive performances are also assessed in symmetric electrochemical cell configuration. The nanorodpedal MnO2 anchored on the nitrogen doped graphene (NRG/MnO2) has a high specific capacitance of 183 F/g with 97% retention after 1000 galvanostatic charge/discharge cycling. The high capacitance and good cycling stability of NRG/MnO2 are attributed to the suitable phase and nano-petal morphology of MnO2 in addition to the enhanced conduction and good anchoring substrate due to the presence of NRG.