Electrochemical oxidation of Mn/MnO films: formation of an electrochemical capacitor

An in-depth study of the oxidation step required to produce electrochemical capacitors from porous manganese-oxide materials was carried out. The oxidation process takes place under the application of a small anodic current in a solution of 1 M Na 2SO 4, resulting in the formation of a three-layered...

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Bibliographic Details
Published in:Acta materialia 2005-02, Vol.53 (4), p.957-965
Main Authors: Djurfors, B., Broughton, J.N., Brett, M.J., Ivey, D.G.
Format: Article
Language:English
Subjects:
Applied sciences
Corrosion
Corrosion environments
Electrochemical supercapacitor
Exact sciences and technology
Manganese oxide
Metals. Metallurgy
Physical vapor deposition
Transmission electron microscopy
XPS
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Summary:An in-depth study of the oxidation step required to produce electrochemical capacitors from porous manganese-oxide materials was carried out. The oxidation process takes place under the application of a small anodic current in a solution of 1 M Na 2SO 4, resulting in the formation of a three-layered structure. During the oxidation process, a base layer of undisturbed zigzag material oxidizes from Mn/MnO to Mn 3O 4. At the same time, a second layer forms directly on the surface of the zigzag material. The layer is partly crystalline Mn 3O 4 and partly amorphous. The final and most important layer is the amorphous, hydrated MnO 2 surface film. It is believed that this layer is solely responsible for the capacitive behavior of these films. The porosity of the electrode prior to oxidation is shown to be immaterial as oxidation of a fully dense film results in similarly high capacitive values attributed to the formation of a porous surface layer.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2004.10.041