| Electrochemistry of oxygen in concentrated NaOH solutions: solubility, diffusion coefficients, and superoxide formation. | |
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MedLine Citation:
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PMID: 19063634 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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The diffusion coefficient (D(O(2))), solubility (C(O(2))), and electrochemical behavior of oxygen reduction were investigated by cyclic voltammetry and transient amperometry on a Pt ultramicroelectrode in aqueous solutions containing various concentrations of NaOH (1-12 M). The results show that both D(O(2)) and C(O(2)) decrease as the solution viscosity (eta) increases significantly with increasing concentration of NaOH. The Stokes-Einstein relationship (D(O(2)) vs 1/eta) is followed, yielding a radius for the O(2) molecule, 2.8 A, that does not change over the concentration range of NaOH studied. From results reported previously for C(O(2)) in more dilute NaOH solutions and the new results here, the number of electrons, n, involved in the first step of the oxygen reduction reaction (ORR) was found to change with the concentration of NaOH, from n = 2 at low NaOH concentrations (1-2 M) to n = 1 at high concentrations (>6 M), in line with the changing water activity. Scanning electrochemical microscopy (SECM) was employed as a sensitive tool to investigate the electrochemical behavior of the product of the ORR in 10 M NaOH solution, O(2)(*-), as a function of potential. The SECM approach curves depend on the substrate bias and state of the Pt substrate surface, and the apparent rate constant for the redox couple of O(2)/O(2)(*-) is determined to be about 2.6 x 10(-4) cm/s in this solution. |
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Authors:
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Cunzhong Zhang; Fu-Ren F Fan; Allen J Bard |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Journal of the American Chemical Society Volume: 131 ISSN: 1520-5126 ISO Abbreviation: J. Am. Chem. Soc. Publication Date: 2009 Jan |
Date Detail:
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Created Date: 2009-01-08 Completed Date: 2009-03-23 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 7503056 Medline TA: J Am Chem Soc Country: United States |
Other Details:
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Languages: eng Pagination: 177-81 Citation Subset: - |
Affiliation:
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Center for Electrochemistry, Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712-0165, USA. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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