Nanostructures and Capacitive Characteristics of Hydrous Manganese Oxide Prepared by Electrochemical Deposition

Amorphous manganese oxide deposits with nanostructures (denoted as were electrochemically deposited onto graphite substrates from 0.16 M with pH 5.6 by means of the potentiostatic, galvanostatic, and potentiodynamic techniques. The maximum specific capacitance of deposits plated in different modes, measured from cyclic voltammetry at 25 mV s −1 , is about 230 F g −1 in a potential window of 1.0 V. The high electrochemical reversibility, high-power characteristics, good stability, and improved frequency responses in 0.1 M for these nanostructured deposits prepared by electrochemical methods demonstrate their promising potential in the application to electrochemical supercapacitors. The nanostructure of clearly observed by means of a scanning electron microscope, was found to depend strongly on the deposition mode. The similar capacitive performance of all deposits prepared in different modes was attributable to their nonstoichiometric nature with a very similar oxidation state, demonstrated by XPS spectra. © 2003 The Electrochemical Society. All rights reserved.