Microwave synthesis : characterization and electrochemical properties of amorphous activated carbon-MnO2 nanocomposite electrodes

Abstract

The green chemistry route (Microwave) has been used to produce nanocomposite materials based on activated carbon (AC) and manganese (Mn) oxide nanostructures. XRD analysis revealed that amorphous and crystalline oxide structures were synthesized. Morphological studies reveal rod-like α-MnO2 for the pristine sample, while cubic Mn3O4 and irregular shaped MnO2 structures were anchored on the AC substrate as revealed by the scanning electron microscopy (SEM) showing that the nanostructures were uniformly distributed on AC. The electrochemical tests of the composites as electrodes show that the amorphous ACMnO2 had a specific capacitance of 180 F g−1, nearly four times higher than that of crystalline AC-Mn3O4 composite electrode (55 F g−1). The Coulombic efficiency for the AC-MnO2 cell was 98 % after 5000 cycles indicating a small capacitance loss. The green route technique and good electrochemical properties indicate that the amorphous AC-MnO2 nanocomposite could be a good material for high-capacity, low-cost, and environmentally friendly electrodes for electrochemical capacitors.