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

The green chemistry route (microwave) was 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. Scanning electron microscopy studies revealed rod-like α-MnO2 for the pristine sample, while cubic Mn3O4 and irregularly shaped MnO2 structures anchored on the AC substrate, with the nanostructures being uniformly distributed on the AC. The electrochemical tests of the composites as electrodes showed that the amorphous AC-MnO2 had a specific capacitance of 180 F g−1, nearly four times higher than that of the crystalline AC-Mn3O4 composite electrode (55 F g−1). The coulombic efficiency for the AC-MnO2 cell was 98% after 5000 cycles, indicating only a small loss of capacitance. 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.