Low temperature electrochemistry

Breiter, M. W. Low-Temperature Electrochemistry at High-T2 Superconductor/Ionic Conductor Interfaces 28... 

Although the effect of temperature on each of the steps in an overall electrode process is readily predictable, it is surprising to find in the literature very few systematic studies of this variable or attempts to use it to change the rate, products or selectivity of an organic electrosynthetic process. A recent paper has, however, discussed equipment and suitable solvents for low-temperature electrochemistry (Van Dyne and Reilley, 1972a). 

The low-temperature electrochemistry technique is useful in the study of electrode reactions involving unstable products or intermediates. Lowering the temperature by 30-40 °C decreases the reaction rate of the unstable species to one-tenth of the original value. It is equivalent to a ten-fold increase in the voltage scan rate. Figure 8.22 shows the effect of temperature on the cyclic voltammo-gram for the oxidation of 1,2,3,6,7,8-hexahydropyrene. At ambient temperatures, it does not give a re-reduction peak Fiowever, at -60 °C, reversible oxidation and rereduction waves are observed. The techniques of low-temperature electrochemistry... 

This immediately leads to a question How small must these excursions be in order for the predictions to be valid Theoretically, the answer is zero millivolts, a clever but uninteresting answer. Practically the answer usually found in the literature is between 8/n and 12/n mV where n is the number of electrons transferred in the electrochemical reaction. These numbers are arrived at by estimating what kind of deviation from theoretical behavior can be detected experimentally. For purposes of this discussion we will use 10 mV. At this point it is useful to remember that the exponential terms are of the form anF(E - E°)RT, where T is the absolute temperature and a is either a or 1 - a. The 10/n mV figure is based on an a of 0.5 at 25 °C. Any change in these parameters from their nominal value would influence this limit (particularly in the case of low-temperature electrochemistry in nonaqueous solvents). This leads to the obvious next question What happens if you exceed this limit The answer is that the response begins to deviate noticeably from the ideal, theoretical model. How great the deviation is depends upon how far one exceeds... 

A summary of some of the solvent/electrolyte systems that have been used for low-temperature electrochemistry is given in Table 16.2. The lowest tem-... 

Other nitriles, aliphatic and aromatic, have been investigated as solvents for electrolysis. Butyronitrile has been suggested as the solvent of choice for low-temperature electrochemistry [86], and propionitrile has in some cases been employed, as it is less... 

Katayama Y, Yokomizn M, Miura T et al (2001) Preparation of a novel fluorosilicate salt for electrodeposition of silicon at low temperature. Electrochemistry 69 834-840... 

LOW TEMPERATURE ELECTROCHEMISTRY AND SPECTROELECTROCHEMISTRY OF TRANS-TETRACARBONYLBIS(ALKENE) TUNGSTEN(O) COMPLEXES... 

Low Temperature Electrochemistry and Spectroelectrochemistry of Catalytically Important Tungsten(0) Complexes M. Wlgodd. T. Szymanska-Buzar. M. JaroszewsM and J.J. Zolkowski... 

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