Pulse electrodeposited manganese oxide on carbon fibers as electrodes for high capacity supercapacitors

Arrays of manganese dioxide (MnO2), a pseudocapacitive material, have been deposited on the carbon fibers (CF) of a carbon woven fabric by electrodeposition from a solution containing manganese sulfate and sulfuric acid using galvanostatic square waves. The thickness of the MnO2 was varied by increasing/decreasing the time of deposition, and the electrochemical performance of the MnO2 has been analyzed. The CF serves as a substrate material with high surface area, good electrical conductivity and excellent mechanical strength. The electrochemical properties of the resultant electrode were examined by cyclic voltammogram (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy in a three-electrode system. From the specific capacitance calculations obtained from CV and charge-discharge, a high specific capacitance of 769 F g−1 @ 5 mV s−1 (low weight electrode) has been achieved. The maximum area capacitance, estimated from the charge-discharge curves, was 790 mF cm−2 @ 5 mV s−1. The high-performance is attributed to the double layer capacitance of the CFs combined with the pseudocapacitive nature of MnO2, the large surface area, and high degree of ordering of the ultrathin MnO2.