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Method for Determination of the Kinetic Parameters in Electrolytes Containing Surface‐Active Substances, Accounting for the Influence of Electrode Potential on the Changes of the Free Electrode Surface
Author(s) -
Lazarov Veselin,
Stoychev Dimitar
Publication year - 2004
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200402776
Subject(s) - electrode , electrode potential , dropping mercury electrode , electrolyte , chemistry , reference electrode , adsorption , palladium hydrogen electrode , standard hydrogen electrode , working electrode , electrochemistry , standard electrode potential , reversible hydrogen electrode , analytical chemistry (journal) , overpotential , thermodynamics , materials science , chromatography , physics
Based on the generally accepted concept of the influence exerted by the value of the electrode potential on the degree of coverage of the electrode surface with molecules of the adsorbed surface‐active substance (SAS), an equation has been derived in the present paper which meets the requirement of consistency in stability of the electrode surface and allows for calculating the kinetic parameters of an irreversible electrochemical process, such as they would have been if the value of the electrode potential did not influence the size of the free (uncoated) electrode surface. The method is based on the substantial difference between the rates of charging of the double electric layer and of establishing adsorption equilibrium on the electrode surface. In the general case of adsorption of organic molecules this difference is about 4 orders of magnitude, which gives grounds for the assumption that within the short time from the start of the galvanostatic pulse till the onset of a Faraday process the electrode surface remains unchanged, i.e., such as it has been at the equilibrium potential. The method is illustrated by processing of the experimental data for two SAS widely used in the industrial practice, which yield a sufficiently long transition time ( τ >5 s) and at the same time change more or less the overpotential of the electrochemical process. The electric charge of the electrode changes its sign at that, which is an indication of the applicability of the method in the potential regions in which SAS are desorbed as well.