Variations in MnO2 electrodeposition for electrochemical capacitors

Results are presented from an electrochemical investigation into properties of hydrous MnO2 grown by electrodeposition from aqueous solution. MnO2 grown from MnSO4 solutions mixed with acetate based electrolytes has been studied for electrochemical capacitor applications. The addition of acetates to the electrodeposition solution permits a controllable reduction in the deposition potential from roughly 0.95 to 0.55 V under galvanostatic conditions. We can observe some morphological changes in the material under SEM examination when different acetate solutions are used but the capacitance appears to be insensitive to this variable. We have grown material under both potentiostatic and galvanostatic conditions for comparison. We have observed a consistent insensitivity in specific capacitance for material deposited under potentiostatic conditions at 1 V in comparison to galvanostatic depositions occurring in the 0.55 V range. We have also observed a consistent decrease in specific capacitance from 260 to 50 F/g as material thickness increases.