Synthesis of MnO2 nanowires and their capacitive behavior in aqueous electrolytes containing magnesium ions

Abstract

Manganese dioxide nanowires with different diameters have been synthesized through a simple hydrothermal method. The morphology and microstructure of MnO2 nanowires were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The electrochemical studies showed that the capacitance of MnO2 nanowires with a smaller diameter is much higher than that with a larger diameter whether MgSO4 or Mg(NO3)2 electrolytes are used, both of which are higher than those based on Na2SO4 and Al2(SO4)3 electrolytes. Excellent stability, even more than 100% capacitance retention after 1000 cycles for the short MnO2 nanowire sample, was observed in electrolytes containing magnesium ions. The energy storage mechanisms of MnO2 nanowires in electrolytes containing multivalent and monovalent metal ions have been proposed based on the experimental results.