Scanning probe techniques electrochemical applications

The atomic surface order is described in terms of a simple unit cell and techniques for the preparation of surfaces with defined atomic order are well established. The description of mesoscopic structures is not as straightforward for a single-crystal surface mesoscopic properties can be, e. g., terrace widths and step densities, for dispersed electrodes the size and distribution of particles. Real-space information under in-situ electrochemical conditions is required for the characterization of such mesoscopic properties. This information can only be derived from the application of scanning probe techniques, which were introduced to electrochemistry in the mid-1980s and give high-resolution real-space images of electrode siufaces under in-situ electrochemical conditions. 

Localized forms of corrosion (such as pitting, crevice, and galvanic corrosion) arise when the metal surface is not compositionally uniform and/or when there is not a uniform exposure of the metal surface to the corrosive environment [6], Such localized forms of corrosion lead to nonuniform current density distribution across the metal surface as well as nonuniform distribntions of species concentration (such as metal ions, H+, and Oj). For these localized forms of corrosion, the scanning probe techniques provide valuable spatial and temporal information not available from the surface-averaging (or global) techniques mentioned earlier. A brief review of scanning probe techniques as applied to localized corrosion studies has recently appeared [7]. We have recently prepared a very extensive review chapter for Volume 24 of Electroanalytical Chemistry A Series of Advances [8], and the reader is referred to that chapter for more in-depth discussion of the application of these techniques in corrosion research. In Section 14.2, we provide an overview of several scanning electrochemical probe techniques used in corrosion research. In Section 14.3, we describe... 

The development of local probe techniques such as Scanning Tunneling Microscopy (STM) or Atomic Force Microscopy (AFM) and related methods during the past fifteen years (Nobel price for physics 1986 to H. Rohrer and G. Binning) has opened a new window to locally study of interface phenomena on solid state surfaces (metals, semiconductors, superconductors, polymers, ionic conductors, insulators etc.) at an atomic level. The in-situ application of local probe methods in different systems (UHV, gas, or electrochemical conditions) belongs to modem nanotechnology and has two different aspects. 

The application of X-ray methods to electrochemical studies is still in its infancy. The need for synchrotron radiation, rather sophisticated cells, and elaborate data interpretation has limited the use of these techniques. However, the atomic-level structural information that these methods provide is rivaled only, perhaps, by the scanning probe methods (Chapter 16) and suggests that wider application of X-ray methods is in the offing. 

The properties and applications of microelectrodes, as well as the broad field of electroanalysis, have been the subject of a number of reviews. Unwin reviewed the use of dynamic electrochemical methods to probe interfacial processes for a wide variety of techniques and applications including various flow-channel methods and scanning electrochemical microscopy (SEM), including issues relating to mass transport (1). Williams and Macpherson reviewed hydrodynamic modulation methods and their mass transport issues (2). Eklund et al. reviewed cyclic voltammetry, hydrodynamic voltammetry, and sono-voltammetry for assessment of electrode reaction kinetics and mechanisms with discussion of mass transport modelling issues (3). Here, we focus on applications ranging from measnrements in small volumes to electroanalysis in electrolyte free media that exploit the uniqne properties of microelectrodes. 

The following sections cover the preferred electrochemical aspects of the formation and the materials properties of the investigated monomers and their relatives as revealed with spectroscopic and surface sensitive methods. Results obtained with other methods (scanning probe microscopies and, especially, traditional electrochemical techniques) are quoted only in passing when deemed necessary for a better understanding of the spectroelectrochem-ical results. Because of the numerous reviews that cover a very broad range of conceivable and potential applications, no attention is paid to this aspect. 

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