Supramolecular assisted fabrication of Mn3O4 anchored nitrogen-doped reduced graphene oxide and its distinctive electrochemical activation process during supercapacitive study

Mn3O4 anchored nitrogen-doped reduced graphene oxide is fabricated via a facile hydrothermal route by using the Mn2+-GO supramolecular system as precursor and the ammonia as precipitant and nitrogen source. A combined characterization method including UV-vis absorption spectrum, fluorescence spectrum, and zeta potential and particle sizing measurement is adopted to study the interactions between Mn2+ and GO nanosheets. More importantly, the electrochemical activation process of the Mn3O4/N-rGO electrode in 1 mol L−1 Na2SO4 is investigated in detail. It is found that the activation process originates from the conversion of structure and morphology from spinel Mn3O4 to nano-structured birnessite MnO2. The activation process mainly occurs in the first 200 cycles, in which the specific capacitance increases by 88.2%. The electrochemical experimental results indicate that the Mn3O4/N-rGO electrode after the activation process exhibits improved capacitive performances with a specific capacitance of 141 F g−1 at 0.2 A g−1 and a superior cycle stability (90.3% capacitance retention after 5000 cycles). This study will give a further insight into the distinctive electrochemical activation process and the supercapacitive properties of Mn3O4-based materials.