Ideal capacitive behavior of hydrous manganese oxide prepared by anodic deposition

Amorphous hydrous manganese oxide (a-MnO2.nH(2)O) was anodically deposited onto a graphite substrate from a MnSO4.5H(2)O solution with pH of 6.4. The specific capacitance of this thick a-MnO2.nH(2)O deposit, measured from both cyclic voltammetry and chronopotentiometry, is about 265-320 F g(-1) in a potential window of 1.0 V. The electrochemical reversibility of redox couples at/within the a-MnO2.nH(2)O was significantly influenced by the pH of the test electrolytes. This amorphous hydrous oxide exhibited ideal capacitive behavior (acceptable capacity, high reversibility and high pulse charge-discharge property) between 0 and 1.0 V in 0.1 M Na2SO4 indicating a promising electrode material for electrochemical supercapacitors. (C) 2002 Elsevier Science B.V. All rights reserved.