In situ Co K-edge X-ray absorption fine structure of cobalt hydroxide film electrodes in alkaline solutions

Structural and electronic properties of electrodeposited Co(OH){sub 2} films on Au electrodes in alkaline solutions have been characterized in situ by Co K-edge X-ray absorption spectroscopy (XAS). The results obtained have shown that freshly prepared films undergo spontaneous partial and irreversib...

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Bibliographic Details
Published in:Journal of the Electrochemical Society 2000-12, Vol.147 (12), p.4594-4597
Main Authors: TOTIR, Dana, MO, Yibo, KIM, Sunghyun, ANTONIO, Mark R, SCHERSON, Daniel A
Format: Article
Language:English
Subjects:
ABSORPTION SPECTROSCOPY
Chemistry
COBALT HYDROXIDES
ELECTROCHEMISTRY
ELECTRODEPOSITED COATINGS
Electrodeposition
ELECTRODES
Exact sciences and technology
General and physical chemistry
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
OXIDATION
REDUCTION
Study of interfaces
X-RAY SPECTROSCOPY
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Summary:Structural and electronic properties of electrodeposited Co(OH){sub 2} films on Au electrodes in alkaline solutions have been characterized in situ by Co K-edge X-ray absorption spectroscopy (XAS). The results obtained have shown that freshly prepared films undergo spontaneous partial and irreversible oxidation in 1 M KOH solution even when polarized at -0.58 V vs. Hg/HgO,OH{sup -}, as evidenced by the presence of contributions (ca. 20%) from Co-O and Co-Co shells in the extended X-ray absorption fine structure (EXAFS) attributed to CoOOH. Subsequent polarization of the electrode at +0.6 V oxidizes a significant fraction, but not all of the Co(OH){sub 2} into CoOOH, as judged by the occurrence of Co-O and Co-Co shells in the EXAFS ascribed to Co(OH)2. Further reduction of the same film at -0.58 V vs. Hg/HgO,OH{sup -} increased the amount of Co(OH){sub 2} from 28 to 43%, indicating that the fraction of electrochemically active sites does not exceed ca. 15%. On this basis, the redox activity of Co hydroxide is probably associated with surface rather than bulk Co{sup 2+}/Co{sup 3+} sites in the lattice. These results suggest that Co(OH){sub 2} present as a distinct pure phase in technical Ni oxide electrodes does not contribute significantly to charge storage during cycling, nor to changes in the redox properties of the electrochemically active material.
ISSN:0013-4651
1945-7111
DOI:10.1149/1.1394107