Fabrication and Characteristics of Various Graphene/Manganese Oxide Nanocomposites in Structure, Morphology, and Supercapacitors

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.