Unconventional symmetry factor and transfer coefficient for oxygen reduction at Ir electrodes and their possible use as diagnostic criteria in mechanistic analysis

Oxygen reduction at iridium electrodes in acid solutions is characterized by two linear E-log i regions. In the high current-density (c.d.) region with the Tafel slope of -120 mV, an unconventional symmetry factor is observed. It increases as temperature increases according to beta = betaoT. In the...

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Bibliographic Details
Published in:Journal of the Electrochemical Society 1987-04, Vol.134 (4), p.845-848
Main Authors: SEPA, D. B, VOJNOVIC, M. V, STOJANOVIC, M, DAMJANOVIC, A
Format: Article
Language:English
Subjects:
Chemistry
Electrochemistry
Exact sciences and technology
General and physical chemistry
Kinetics and mechanism of reactions
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Summary:Oxygen reduction at iridium electrodes in acid solutions is characterized by two linear E-log i regions. In the high current-density (c.d.) region with the Tafel slope of -120 mV, an unconventional symmetry factor is observed. It increases as temperature increases according to beta = betaoT. In the low c.d. region with the Tafel slope of -60 mV, the transfer coefficient is also unconventional. It increases with temperature according to alpha = alphaoT. Such a transfer coefficient is not compatible with a slow chemical step as rate determining following first electron transfer step. It is compatible with slow first charge transfer step under Temkin adsorption condition. It is suggested that this transfer coefficient is a sum of two symmetry both of which increase with temperature according to beta = betaoT.
ISSN:0013-4651
1945-7111
DOI:10.1149/1.2100584