Green synthesis of MnO x nanostructures and studies of their supercapacitor performance

Manganese oxides with different crystalline phases and morphologies were prepared by calcining MnCO3 precursors. The MnCO3 precursors with different morphologies were obtained through a green route under hydrothermal conditions with orange pericarp extracting solution as the reducing agent. By calcining the precursor under different temperatures and atmospheres, MnO (x) with different stoichiometric ratios (i.e., MnO, MnO2, Mn2O3, and Mn3O4) can be obtained. Electrochemical studies reveal that among these manganese oxides, MnO or MnO2 are more suitable as supercapacitor working electrodes than Mn2O3 or Mn3O4. They exhibit high specific capacitance up to 296.6 F/g and also possess good cycling stability, which make them potential electrode materials for supercapacitors.