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Charge transfer reactions on oxide‐covered Ti Electrodes: Effect of dielectric constant variation and oxide stabilization
Author(s) -
Rahim M. A. Abdel,
Rahman Amal A. Abdel,
Khalil M. W.
Publication year - 1996
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/mawe.19960270908
Subject(s) - oxide , exchange current density , tafel equation , redox , charge transfer coefficient , chemistry , electron transfer , reaction rate constant , analytical chemistry (journal) , anode , kinetics , cathodic protection , electrode , dielectric , inorganic chemistry , electrochemistry , materials science , cyclic voltammetry , physics , optoelectronics , organic chemistry , quantum mechanics , chromatography
The electron transfer kinetics of the Fe 3+ /Fe 2+ redox couple on the oxide covered Ti electrodes were investigated as a function of the film thickness, film stabilization, and concentration of the redox species. The oxides were formed potentiodynamically in acidic solution of pH=3 (Na 2 SO 4 +H 2 SO 4 ) at a scan rate of 1 mV s −1 . The cathodic and anodic Tafel lines were also measured at the same scan rate. The logarithm of the exchange current density i 0 shows an exponential decrease with the oxide film thickness. Direct tunnelling may explain the kinetics of the reaction across thin Ti0 2 (oxide formed at the potential region before the O 2 ‐evolution). Values of the cathodic and anodic transfer coefficients are tabulated. It was found that, the stabilization of the oxide could possibly increase its conductivity. The electron transfer reaction showed a first order dependence on the redox species concentration, independent of the conditions of oxide film formation.