Introduction of MnO2 nanoneedles to activated carbon to fabricate high-performance electrodes as electrochemical supercapacitors

Synthesis of activated carbon/MnO2 composites for use as high-performance materials in supercapacitors is reported by the following synthetic procedure: first, activated carbon was thermally treated to create oxygen-containing functional groups in order to provide anchor sites between the activated carbon and MnO2 nanoneedles. Formation of MnO2 nanoneedles was subsequently achieved on the activated carbon surface. Characterizations indicated that the MnO2 nanoneedles in the composite were homogeneously dispersed on the thermally treated activated carbon surface. Before fabricating activated carbon/MnO2 composites, the extent of the oxidation of the activated carbon was determined. The electrode made from the activated carbon subjected to 6 h of thermal treatment (AC6) showed the highest specific capacitance (90.5 F g−1), which was attributed to the fast redox process caused by the oxygen functional groups. The specific capacitance of the AC6/MnO2 composite formed with a MnO2/AC6 feeding ratio of 3:1 (AC6/MnO2(3)) showed the highest value among the AC6/MnO2 composite electrodes fabricated, which was attributed to the synergistic effect of both the activated carbon porous structure and redox reaction of the MnO2 nanoneedles. This procedure is a promising fabrication method for supercapacitor electrodes.