Rapid synthesis of graphene/amorphous α-MnO2 composite with enhanced electrochemical performance for electrochemical capacitor

• Graphene/MnO2 is successfully fabricated by a facile co-precipitation method.
• The graphene/MnO2 electrode reaches 367 Fg−1 in 1 M KOH electrolyte.
• The electrode exhibits good cycling performance of 73.9% retention after 1000 cycles.

Nanostructured graphene/amorphous α-MnO2 composites have been synthesized by a facile co-precipitation method under the alkaline condition, in which graphene nanosheets as a supporting substrate to grow MnO2. Characterizations of prepared samples’ morphology and microstructures indicate MnO2 is successfully formed on the surface of graphene by electrostatic interaction. Moreover, the electrochemical properties of the synthesized electrode materials for supercapacitors are studied in a three-electrode experimental setup using a 1 M KOH aqueous solution as the electrolyte. As a result, the specific capacitance of graphene/MnO2 composite (weight ratio of graphene to MnO2 is 1:1) determined by a galvanostatic charge–discharge method at a current density of 1 Ag−1 reaches 367 Fg−1, which is 1.8 and 4.6 fold higher than that of pure graphene and MnO2. The capacity retention of the graphene/MnO2 composite is 73.9% of the original capacitance after 1000 cycles, indicating graphene/MnO2 composite is a promising electrode material for supercapacitors.