Square-wave voltammetry reversible redox processes

One aspect that reflects the electronic configuration of fullerenes relates to the electrochemically induced reduction and oxidation processes in solution. In good agreement with the tlireefold degenerate LUMO, the redox chemistry of [60]fullerene, investigated primarily with cyclic voltammetry and Osteryoung square wave voltammetry, unravels six reversible, one-electron reduction steps with potentials that are equally separated from each other. The separation between any two successive reduction steps is -450 50 mV. The low reduction potential (only -0.44 V versus SCE) of the process, that corresponds to the generation of the rt-radical anion 131,109,110,111 and 1121, deserves special attention. 

DC) of a surface-confined redox process - at 298.2 K the half-peak-width for a reversible process is 90.6/n in mV where n is the number of exchanged electrons if there are no interactions between the adsorbed species (sites). In the case of attractive interactions is smaller, while at repulsive interactions its value is higher than 90.6 mV [i]. Peaks are also produced by AC and -> square-wave voltammetry of solution-based as well as surface-confined redox species, and by - stripping analysis and other techniques [i-iii]. 

Theoretical modeling for redox processes in ion insertion solids predicts that, in the presence of a sufficiently high concentration of electrolyte, the voltammetric response of electroactive centers attached to porous materials will be similar, in the case of reversible electron transfer processes, to that displayed by species in solution (Lovric et al., 1998). Figure 2.7 shows the square-wave voltammetry (SQWV)... 

Finally, other types of voltammetric experiments may be employed beneficially for the characterisation of the redox properties of redox active compounds. Figure H.l.lbd shows square wave voltammograms [72] for the oxidation and reduction of the binuclear ruthenium complex. Well-defined peak responses indicate the presence of a reversible redox process. In this situation, the peak position corresponds closely to the reversible potential for the process and the peak height is related to the number of transferred electrons. Square-wave voltammetry may be employed to enhance reversible redox processes and to discriminate against irreversible and background processes (see also Chap. II.3). 

The above treatment assumes that the measured reduction potentials are thermodynamically meaningful. Although redox potentials can be measured by a variety of electrochemical techniques, cyclic voltammetry, differential pulse polarography, and more recently, square wave voltammetry have found the greatest use because of the ability of these techniques to reveal the dynamics of the associated chemical processes, and hence access the chemical and electrochemical reversibility of the couple. Chemical and electrochemical reversibility have been defined and problems associated with the distinction between these terms have been covered in Chapter 2.15 (2.15.2.2.1), however, for the purpose of this discussion it is useful to treat these behaviors separately. 

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