Localized electrochemical impedance

Measixrement techniques Bridge mechanical generator Bridge electronic generator Impulse method, oscillograph, Laplace transform Analogue impedance measurement, potentiostat (AC + DC) Digital impedance measurement, cormection with computer Local electrochemical impedance spectroscopy (LEIS)... 

Remember 7.4 Local Electrochemical Impedance Spectroscopy (LEIS) is a relatively new and underutilized technique that is useful for exploring the influence cf surface heterogeneities on the impedance response. 

R. S. Lillard, R J. Moran, and H. S. Isaacs, "A Novel Method for Generating Quantitative Local Electrochemical Impedance Spectroscopy," Journal of The Electrochemical Society, 139 (1992) 1007-1012. 

Recently, two new electrochemical mapping techniques have become available the scanning vibrating electrode technique (SVET) and the localized electrochemical impedance spectroscopy (LEIS) technique. These techniques provide the capability to identify and monitor electrochemical behavior down to the micron level. These represent significant advances over traditional electrochemical methods (cyclic voltammetry, EIS, and even EQCM), which provide data that reflect only an average over the entire sample surface. Although such data are very useful, a major drawback is that no local or spatial information is obtained. 

The advent of ever smaller electrochemically cells (microcells, capillary cells) which can be placed on selected areas of an electrode surface allows spatially resolved measurements of local properties. Spectroscopic methods modified in such a way like e.g. locally resolved electrochemical mass spectrometry have been treated in previous sections. Optical methods incorporating scanning probes wiU be treated below. Classical electrochemical methods like e.g. impedance measurements employing these miniaturized cells [1] thus providing localized information will not be treated in this book. The same applies to scanning electrodes employed in localized electrochemical impedance measurements (LEIS). 

B.B. Katemann, A. Schulte, E.J. Calvo, M. Koudelka-Hep, W. Schuhmann, Localized electrochemical impedance spectroscopy with high lateral resolution by means of alternating current scanning electrochemical microscopy, Electrochem. Commun. 4 (2002) 134-138. 

G. Baril, C. Blanc, M. Kedam, N. Pebere, Local electrochemical impedance spectroscopy applied to the corrosion behavior of an AZ91 magnesium alloy, J. Electrochem. Soc. 150 (2003) B488-B493. 

V.M. Huang, S. Wu, M.E. Orazem, N. Pebere, B. TriboUet, V. Vivier, Local electrochemical impedance spectroscopy a review and some recent developments, Electrochim. Acta 56 (2011) 8048-8057. 

Lillard and coworkers developed a method called Local Electrochemical Impedance Spectroscopy LEIS [39). It relies on the fact that ac current densities in the solution very near to the working electrode are proportional to the local impedance properties of the electrode. In order to determine the current densities normal to the surface, the ac potential drop was measured between planes parallel to the electrode surface employing a two-electrode microprobe. A schematic of a commercially available experimental setup for LEIS is... 

Wittmann, M.W., R.B. Leggat, and S.R. Taylor. 1999. The detection and mapping of defects in organic coatings using local electrochemical impedance methods. J Electrochem Soc 146 (11) 4071. 

Lillard R. S., Kruger J., Tait W. S. Moran P. J. (1995). Using local electrochemical impedance spectroscopy to examine coating failure. Corrosion, Vol. 51, No. 4, pp. 251-259 ISSN 0010-9312. 

E. Bayet, F. Huet, M. Keddam, K. Ogle, and H. Takenouti, A novel way of measuring local electrochemical impedance nsing a single vibrating probe, J. Electrochem. Soc. 144-U 1 (1997). 

The local electrochemical impedance spectroscopy (LEIS) " is another scanning probe technique that can map the ac impedance distribution over an electrode surface. In LEIS a sinusoidal voltage perturbation between the working and reference electrode is maintained by driving an ac current between the working... 

R. S. Lfllard, R J. Moran and H. S. Isaacs, Novel method for generating quantitative local electrochemical impedance spectroscopy , J. Electrochem. Soc. 139, 1007 (1992). 

Microcapillaiy electrochemical cells are widely used in biology for local potential measurements at a very reduced size. In corrosion, pioneering work was performed for promoting the Scanning Reference Electrode Technique (SRET) in this case the microcapil-laiy is immersed in the bulk electrolyte and local potential or local electrochemical polarization or local electrochemical impedance has been measnred. 

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