Non-aqueous electrochemistry

Aurbach, D., ed., Non-aqueous Electrochemistry, Marcel Dekker, New York, 1999. 

Recently, applications of lion-aqueous solutions in the field of modern electrochemical technologies are increasing. Books [1] and review articles [2] that deal with the technological aspects of non-aqueous electrochemistry have appeared. In this chapter, examples of such applications of non-aqueous solutions are outlined. In the last section, the electrochemical use of supercritical fluids and ionic liquids as environmentally benign media is also discussed. 

Because water is ubiquitous both in the sensing environment and inside many sensors (especially electrochemical sensors), the hydrophobic or hydrophilic nature of a polymer used in a sensor is often crucial. For example, a polymer that is to be used as a hydrogel is by definition hydrophilic. On the other hand, gas-permeable membranes are often made of hydrophobic polymers to prevent passage of water through the membrane. These conventions are not always the case, however. An electrolyte for a sensor operating with non-aqueous electrochemistry may be less hydrophilic. Similarly, an in situ sensor to analyse polar degradation products in motor oil may use a hydrophilic membrane to allow passage of the analyte into the aqueous electrolyte from the non-polar hydrocarbon sample [14]. 

The second example concerning heat of solution measurements was chosen to stress a crucial problem in non-aqueous electrochemistry. This is the proper extrapolation to infinite dilution when association of the electrolyte occurs . Figure 4 shows that the validity range of the limiting law is attained only at very low concentrations (here <10 M), generally inaccessible to measurements. Hence, extrapolation from measured values (>5 10 M) yields erroneous data. Reliable... 

In aqueous solution a very wide range of electrolytes may be used. Electrochemical studies in non-aqueous solvents [12,13] are, however, very dependent on the use of tetraalkylammonium salts, the large cation making many such salts soluble in organic media. Indeed, it was the development of simple methods of preparation of (C4H9)4N C10 and similar salts which led to the widespread development of non-aqueous electrochemistry (note R4N " XT , X = CIO, BF or PF are made simply by precipitation on mixing aqueous solutions of R4NHSO4 and NaX). 

The solubility, properties in solution, and reactions of a large number of organic compounds in liquid ammonia were reviewed by Smith (1963), and of inorganic substances by lander (1966) and by Lagowski and Moczyganba (1967) and again by Lagowski (1971) in the Symposium on Non-Aqueous Electrochemistry (Paris, July... 

The difference of 10 mV is significant since the ferrocene/ferrocenium redox couple is often used as a redox marker in non-aqueous electrochemistry (acting as an internal reference electrode), including that using room temperature ionic hquids as solvents. The correction for the difference in diffusion coefficients is necessary to give a valid reference scale. 

There are two major interests in the non-aqueous electrochemistry of magnesium (Mg) ... 

Structure formulae of polar-aprotic solvents and salt which are used in non-aqueous electrochemistry. 

Structural formulae and some physical properties of ionic liquids which are important for non-aqueous electrochemistry. 

As such, they represent an intriguing and possibly useful area of non-aqueous electrochemistry that has received relatively little systematic investigation. 

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