Electrodeposition of Manganese Dioxide in Sulfuric Acid Solution

Abstract

The electrodeposition of MnO, has been studied in sulfuric acid solution in the concentration range from 0.5 to 2 mol/l containing Mn²⁺ ion in the concentration range from 0.05 to 1 molfi. The polarization curves by a potential sweep method showed one oxidation wave at the sweep rate faster than 2 'NT/min and two waves at the slower sweep rate. One step wave was attributed to the oxidation of Mn²⁺ to Mn3+. With a decrease in the sweep rate, the deposition of Mn02 was observed and then it could be considered that the second wave appeared when Pt electrode changed to Mn02 electrode.
The current-time curves for a constant potential electrolysis showed an induction period, which became short with rise of the applied potential but long, reversely, above the potential 0.9 V (vs. Hg/Hg2SO₄/N-H₂504). The current increased with the Mn²⁺ ion concentration and the applied potential, but decreased at the Mn2 ion concentration of 0.5 m91// and at the potential more positive than 0.9 V.
From these results it is considered that Mn²⁺ is oxidized to Mng+ and that adsorbed Mns+ is disproportionated to MnO, and Mn²⁺.