Local electrochemical impedance

Schneider I, Scherer G (2006) Fast locally resolved electrochemical impedance spectroscopy in polymer electrolyte fuel cells. European patent EP 1691438 A1... 

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)... 

The methods described in this chapter and this book apply to electrochemical impedance spectroscopy. Impedance spectroscopy should be viewed as being a specialized case of a transfer-function analysis. The principles apply to a wide variety of frequency-domain measurements, including non-electrochemical measurements. The application to generalized transfer-function methods is described briefly with an introduction to other sections of the text where these methods are described in greater detail. Local impedance spectroscopy, a relatively new and powerful electrochemical approach, is described in detail. 

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. 

A conference dedicated to the development of electrochemical impedance spectroscopy techniques was initiated in 1989 in Bombannes, France. The subsequent meetings, held every three years, took place in California (1992), Belgium (1995), Brazil (1998), Italy (2001), Florida (2004), and France (2007). The special issues associated with these conferences provide unique triennial snapshots of the state of impedance research. One driving concern reflected in these volumes is the heterogeneity of electrode surfaces and the correspondence to the use and misuse of constant phase elements. Local impedance spectroscopy, developed by Lillard et al., may prove to be a useful method for understanding this relationship. 

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). 

LEIS Localized (scanning) electrochemical impedance spectroscopy... 

Many different electrochemical and non-electrochemical techniques exist for the study of corrosion and many factors should be considered when selecting a technique. Corrosion rate can be determined by Tafel extrapolation from a potentiodynamic polarization curve. Corrosion rate can also be determined using the Stem-Geary equation from the polarization resistance derived from a linear polarization or an electrochemical impedance spectroscopy (EIS) experiment. Techniques have recently been developed to use electrochemical noise for the determination ofcorrosion rate. Suscephbility to localized corrosion is often assessed by the determination of a breakdown potenhal. Other techniques exist for the determinahon of localized corrosion propagahon rates. The various electrochemical techniques will be addressed in the next section, followed by a discussion of some nonelectrochemical techniques. 

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. 

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