Charge Storage Mechanism of MnO<sub>2</sub> Electrode Used in Aqueous Electrochemical Capacitor
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Abstract
The charge storage mechanism in MnO 2 electrode, used in aqueous electrolyte, was investigated by cyclic voltammetry and X-ray photoelectron spectroscopy. Thin MnO 2 films deposited on a platinum substrate and thick MnO 2 composite electrodes were used. First, the cyclic voltammetry data established that only a thin layer of MnO 2 is involved in the redox process and electrochemically active. Second, the X-ray photoelectron spectroscopy data revealed that the manganese oxidation state was varying from III to IV for the reduced and oxidized forms of thin film electrodes, respectively, during the charge/discharge process. The X-ray photoelectron spectroscopy data also show that Na + cations from the electrolyte were involved in the charge storage process of MnO 2 thin film electrodes. However, the Na/Mn ratio for the reduced electrode was much lower than what was anticipated for charge compensation dominated by Na +, thus suggesting the involvement of protons in the pseudofaradaic mechanism. An important finding of this work is that, unlike thin film electrodes, no change of the manganese oxidation state was detected for a thicker composite electrode because only a very thin layer is involved in the charge storage process.
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The record
- Venue
- Chemistry of Materials
- Topic
- Supercapacitor Materials and Fabrication
- Field
- Materials Science
- Canadian institutions
- Université du Québec à Montréal
- Funders
- —
- Keywords
- Cyclic voltammetryX-ray photoelectron spectroscopyElectrodeThin filmElectrolyteMaterials scienceElectrochemistryAnalytical Chemistry (journal)Inorganic chemistryChemistryChemical engineeringNanotechnologyPhysical chemistryOrganic chemistry
- Has abstract in OpenAlex
- yes