Premium
The Impedance Response of a Passive Film Revisited by a Double Modulation Technique
Author(s) -
AntañoLópez René,
Keddam Michel,
Turmine Mireille,
Vivier Vincent
Publication year - 2019
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201800737
Subject(s) - capacitance , materials science , double layer capacitance , dielectric spectroscopy , differential capacitance , negative impedance converter , relaxation (psychology) , electrode , electrical impedance , constant phase element , analytical chemistry (journal) , modulation (music) , capacitance probe , electrochemistry , chemistry , electrical engineering , voltage , physics , acoustics , psychology , social psychology , chromatography , voltage source , engineering
Abstract The interfacial capacitance measured in electrochemical experiments is usually considered to be independent of the faradaic processes involved at the electrode surface. In this work, we report on the use of a double modulation technique, which allows the simultaneous measurement of electrochemical impedance spectroscopy (EIS) and modulation of the interfacial capacitance transfer function (MICTF). We show that the capacitance ascribed to the response of passive films formed on pure iron electrodes in phosphoric acid solution exhibits two different time‐constants in low frequency domains, namely the response of intrinsic properties of the film linked to charge carriers and a relaxation ascribed to the thickness relaxation of the oxide film. Interestingly, the low frequency limit of MICTF is in good agreement with the capacitance obtained from EIS measurements. A detailed data analysis allows determination of both, the capacitance of the oxide film and the double layer capacitance to the overall capacitance to be measured. This technique thus provides a unique way of analysing the different contributions ascribed to the relaxation of the interfacial capacitance.