A review about the charge conduction process at poly(o-aminophenol) film electrodes

R. TUCCERI

The Open Physical Chemistry Journal

Bentham Science Publishers (www.bentahm.org/open).

Año: 2009 vol. 3 p. 30 - 45

1874-0677

This review, which is divided into two parts, concerns charge-transport and chargetransferprocesses at poly(o-aminophenol) film electrodes. The first part deals with thecase where the solutions contacting poly(o-aminophenol) films only contain ions that donot possess a redox activity (“background electrolyte”). The second part refers to thetransport properties of poly(o-aminophenol) films contacting redox active solutions. Inthe first part, I have attempted to document the most significant evidence, which provesthat the electrochemical behaviour of poly(o-aminophenol) can be explained on thebasis of a chemical reaction coupled with a reversible electron-transfer process. In thisconnection, it was demonstrated that the response of poly(o-aminophenol) is highlydependent on the solution pH. This indicates that protons and electrons take part in theelectrode reaction of the polymer. Different studies about the charge conduction acrosspoly(o-aminophenol) films indicate the existence of a diffusion-limited charge-transportprocess. It was suggested that the transport process might be electron hopping-assistedby the corresponding counterion motion. In this regard, transport parameters, such asapparent or effective diffusion coefficients, have been employed to characterise thewhole charge conduction process at poly(o-aminophenol) film electrodes. In somepapers, electron and ion movements have been separately treated through electron andion diffusion coefficients. It was found that these transport parameters depend not onlyon the type and concentration of the electrolyte solution contacting the polymer film butalso on polymer film thickness. With regard to the electrochemical behaviour of poly(oaminophenol)in the presence of solutions containing redox active couples, it has beenreported that at negative potentials (-0.250 V versus SCE) the polymer can act as amediator in electron-transfer reactions at the polymer½solution interface. However, atpositive potentials (higher than 0.8 V versus SCE) the species dissolves into thepolymer with a partition equilibrium at the film½solution interface.At the end of this review (Section 4) I have tried to collect common and differentviewpoints on the charge conduction process at poly(o-aminophenol) film electrodesreported in the literature. In Section 5 I describe some critical aspects related to chargetransportparameter values extracted from different electrochemical models applied tostudying the polymer. Finally in Section 6, emphasis is laid on the effects of conductionand permeation processes at poly(o-aminophenol) on some of its practical applications,such as those where the polymer acts as an electrochemical sensor.