Impedance Response of a Thin Film on an Electrode: Deciphering the Influence of the Double Layer Capacitance

• Published in: Chemphyschem Vol. 22; no. 13; pp. 1371 - 1378
• Main Authors: Gharbi, Oumaïma, Tran, Mai T. T., Orazem, Mark E., Tribollet, Bernard, Turmine, Mireille, Vivier, Vincent
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 02.07.2021; Wiley-VCH Verlag
• Subjects: Capacitance; Chemical Sciences; Coated electrodes; constant phase element; Dispersion; double layer capacitance; electrochemical impedance spectroscopy; electrochemistry; Frequency domain analysis; interfacial capacitance; Oxide coatings; Protective coatings; Thickness; Thin films; Electrochemistry; Double layer capacitance; Interfacial capacitance; Constant phase element; Electrochemical impedance spectroscopy
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.202100177

The different contributions of the interfacial capacitance are identified in the case of passive materials or thin protective coatings deposited on the electrode surface. The method is based on a graphical analysis of the EIS results to determine both the passive‐film capacitance in the high‐frequency domain and the double‐layer capacitance in the low‐frequency domain. The proposed analysis is shown to be independent of the physicochemical origins of the frequency dispersion of the interfacial capacitances which results, from an analysis point of view of the experimental results, in the use of a constant‐phase element However, for a correct evaluation of the thin‐film properties such as its thickness, the high‐frequency data must be corrected for the double‐layer contribution. In particular, it is shown that if the double‐layer capacitance gives a frequency‐dispersed response, it is necessary to correct the high‐frequency part for the double‐layer constant‐phase elements. This is first demonstrated on synthetic data and then used for the determination of the thickness of thin oxide film formed on Al in neutral pH solution. Double‐layer capacitance redefines interpretation of impedance response: A method based on a graphical analysis of the electrochemical impedance spectroscopy diagrams is presented to determine both the passive‐film capacitance in the high‐frequency domain and the double‐layer capacitance in the low‐frequency domain. Thus, after correction of the double layer contribution, the thin‐oxide film thickness can be measured.