CENTRO DE TECNOLOGIA DE RECURSOS MINERALES Y CERAMICA
Unidad Ejecutora - UE
capítulos de libros
PERMEATION AND REDOX MEDIATION PROCESSES AT POLY(O-AMINOPHENOL) FILM ELECTRODES IN THE PRESENCE OF HYDROQUINONE/P-BENZOQUINONE REDOX SPECIES: A REVIEW ARTICLE
R. TUCCERI, P. M. ARNAL AND A. N. SCIAN
Nova Science Publishers. Inc.
Año: 2011; p. 1 - 40
This review paper describes the different researches carried out in our laboratory to study transport and transfer processes at poly(o-aminophenol) (POAP) film electrodes in the presence of the hydroquinone/p-benzoquinone (HQ/Q) redox couple. The most significant experiments employing different techniques such as Cyclic Voltammetry, Rotating Disc Electrode Voltammetry and Electrochemical Impedance Spectroscopy are described in detail, and the application of existing models and theories that allow extracting charge-transport and charge-transfer parameters are also outlined. While an electron-transfer reaction (mediation reaction) occurs at negative potential values (E < 0.0 V vs. SCE), permeation processes are observed at positive potential values (E > 0.8 V vs. SCE). Freshly prepared poly(o-aminophenol) films were quantitatively deactivated to study how their permeation and charge-transfer processes are affected by the degree of deactivation (c). While for low degrees of deactivation (c < 0.4) it is possible to recover the conductivity of a deactivated POAP film by reactivation in an alkaline solution, high degrees of deactivation lead to an irreversible deterioration of the polymer film. Electrochemical Impedance Spectroscopy applied at negative potential values allowed obtaining dependences of the different transport parameters on the degree of deactivation of the polymer film. While some parameters such as interfacial metal-film and film-solution resistances (Rmf, Refs, Rifs), the high-frequency capacitance (CH) and the redox capacitance (Cp) exhibit a continuous variation without hysteresis between deactivation and reactivation processes within the whole c range, others such as electron and ion diffusion coefficients (De, Di) show not only marked changes of slope from given c values but also hysteresis between consecutive deactivation and reactivation processes. The diffusion rates of the hydroquinone and benzoquinone species across the polymer film are also strongly reduced with the increase in the degree of degradation. This work could be interesting due to the wide range of potential applications of POAP. In this sense, although in practical applications of POAP it is necessary to maintain the conducting properties unaltered, the polymer is subjected to extreme conditions that can cause its partial deactivation. Thus, it seems to be important for electrochemists to know at least how the charge-transport process at POAP films changes with their deactivation.