Electrochemical Studies of Solid Compounds and Materials

Electroanalytical techniques are traditionally associated with studies of solutions however, direct studies of the electrochemistry of solid materials are very tempting because they can give access to a wealth of information, ranging from elemental composition to thermodynamic and kinetic data, from structure-reactivity relations to new synthetic routes. 

Methods describing the electrochemical investigation of solid compounds and materials have significantly expanded to new possibilities over the last two decades. This chapter focuses on the use of a fairly new and straightforward method referred to as voltammetry of immobilized microparticles (VIM). Detailed reviews of the method are available elsewhere [la-c]. Beside applications in fundamental studies, this method proved to be especially valuable for the analysis of solid materials studied in archeometry [Id]. 

In studies which focus on the redox properties of immobilized microparticles, electrode preparation and electrolyte composition are to be carefully considered. Almost any kind of solid electrode may be applied in order to investigate the redox properties of immobilized solid microparticles. However, attention must be drawn to possible catalytic properties of the electrode with respect to the reactions to be studied, and reactions of the electrolyte, which may or may not accompany the reactions of the solids. The surface hardness of the particular electrode should be kept in mind as well. For example, a hard electrode will allow soft or flake-like solids to be 

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The method involves attaching an ensemble of solid microcrystalline particles to the surface of a suitable electrode. The electrode with the so immobilized solid is then transferred to an electrolyte solution and investigated either purely electrochemically or by additional methods. 

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D. A. Fiedler, F. Scholz, Electrochemical studies of solid compounds and materials in Electroanalytical Methods - Guide to Experiments and Applications (Ed. F. Scholz), Springer, Berlin, p. 331. 

Refs. [i] Bruce PG (ed) (1995) Solid state electrochemistry. Cambridge University Press, Cambridge [ii] Gellings PJ, Bouwmeester HfM (eds) (1997) The CRC handbook of solid state electrochemistry. CRC Press, Boca Raton [iii] Maier J (2000) Festkorper - Fehler und Funktion. Prinzipien der Physikalischen Festkorperchemie. Teubner, Stuttgart [iv] Fiedler DA, Scholz F (2001) Electrochemical studies of solid compounds and materials. In Scholz F (ed) Electroanalytical methods. Springer,... 

D. A. Fiedler, F. Scholz, Electrochemical studies of solid compounds and materials... 

Solid-state electrochemistry — is traditionally seen as that branch of electrochemistry which concerns (a) the -> charge transport processes in -> solid electrolytes, and (b) the electrode processes in - insertion electrodes (see also -> insertion electrochemistry). More recently, also any other electrochemical reactions of solid compounds and materials are considered as part of solid state electrochemistry. Solid-state electrochemical systems are of great importance in many fields of science and technology including -> batteries, - fuel cells, - electrocatalysis, -> photoelectrochemistry, - sensors, and - corrosion. There are many different experimental approaches and types of applicable compounds. In general, solid-state electrochemical studies can be performed on thin solid films (- surface-modified electrodes), microparticles (-> voltammetry of immobilized microparticles), and even with millimeter-size bulk materials immobilized on electrode surfaces or investigated with use of ultramicroelectrodes. The actual measurements can be performed with liquid or solid electrolytes. 

Many electrochemical conversions of solid compounds and materials, including for example the corrosion of metals and alloys or the electrochemical conversions of most battery materials, take place within a liquid electrolyte environment, with the classic approach to investigation comprising macro-sized electrodes. However, in order to obtain a comprehensive understanding ofthe mechanism ofthese solid-state electrochemical reactions, the simple technique of immobilizing small amounts of a solid compound/material on an inert electrode surface provides an easy, yet sometimes exclusive, access to their study. In this chapter is presented a survey of the recent developments of this approach, which is referred to as the voltammetry of immobilized microparticles (VIM). Attention is also focused on progress in the field of theoretical descriptions of solid-state electrochemical reactions. 

There are only two requirements for the compounds and materials to be used by VIM They should be highly insoluble in the electrolyte solution used and they must possess electroactivity, i.e., the ability to be either oxidized or reduced in the accessible potential window of the experiment. Most importantly, there is no restriction with respect to the electronic conductivity. Even insulators such as white phosphoms can be studied, because the electrochemical reaction which can take place at the three-phase boundary compound-electrode-solution can often deliver sufficient charge to give measurable currents. One can easily distinguish three different kinds of compounds, those which are not electroactive, those which are irreversibly destroyed in the electrochemical reactions, and those which can be reversibly reduced and oxidized. The latter compounds are characterized by possessing the ability to exchange electrons with the electrode and ions with the solution. This ability requires solid compounds that can house ions through features of their crystal structure, e.g., channels or interlayers. 

The salting-out method as a nanoparticle immobilization on a solid substrate has been applied to the photo-electrochemical study of bio-material, which has a bigger body than organic artificial compound and an essential defect for signal-to-noise ratio. Terasaki et al. used these methods to increase the photo-induced... 

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