Capacitive Behavior and Charge Storage Mechanism of Manganese Dioxide in Aqueous Solution Containing Bivalent Cations

Abstract

Manganese dioxide shows an ideal capacitive behavior in the aqueous solution containing bivalent cations (Ca2+)(Ca2+) . A specific capacitance value as high as 310Fg−1310Fg−1 in 0.1molL−10.1molL−1 Ca(NO3)2Ca(NO3)2 electrolyte was measured at a sweep rate of 2mVs−12mVs−1 . A cycle life test was also performed and no capacity loss of MnO2MnO2 electrode was found after 600cycles600cycles , which indicates the MnO2MnO2 electrode possesses a good cycling property in the aqueous electrolyte containing bivalent cations (Ca2+)(Ca2+) . X-ray photoelectron spectroscopy data reveal that the Ca2+Ca2+ ions in the electrolyte are involved in the charge storage process of manganese dioxide in an aqueous system and correspondingly a part of Mn4+Mn4+ ions will become to Mn3+Mn3+ ion to balance the charge.