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Electrodeposition of manganese dioxide has been examined using a combination of rotating disk electrode (RDE) and rotating ring–disk electrode (RRDE) voltammetry, with the goal of developing an understanding of the electrodeposition mechanism. Experimental variables that have been examined include electrolyte composition (combined changes within the ranges 0.1–1.0 M MnSO 4 and 0.1–5.0 M H 2 SO 4 ), rotation rate (1000–4000 rpm) and temperature (22–98 °C). Voltammetric data (current peak instead of sigmoidal response, and non-proportional current–concentration data) indicates that already deposited manganese dioxide is a poorer catalytic surface compared to Pt. The overall electrodeposition process revolves on the formation of a Mn(III) intermediate, and whether it is soluble for extended periods of time, as in concentrated H 2 SO 4 (>1.0 M), or whether it hydrolyzes rapidly to precipitate as a solid Mn(III) species (e.g. MnOOH) as in more dilute H 2 SO 4 solutions ( |
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