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 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.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC; NIH
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 942840
- Report Number(s):
- ANL/CHM/JA-35141
- Journal Information:
- J. Electrochem. Soc., Journal Name: J. Electrochem. Soc. Journal Issue: 12 ; Dec. 2000 Vol. 147; ISSN JESOAN; ISSN 0013-4651
- Country of Publication:
- United States
- Language:
- ENGLISH
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