Electrochemical properties of poly- ortho-aminophenol modified electrodes in aqueous acid solutions

Abstract

Poly- ortho-aminophenol (PolyoAP) modified electrodes were obtained from the electro-oxidation of the corresponding monomer on platinum and glassy carbon electrodes in aqueous solution. The electrochemical behaviour of the film was studied by cyclic voltammetry under various experimental conditions. At low scan rates ( v<100 mV s −1) the film shows thin-layer behaviour, while at higher rates semi-infinite diffusion behaviour is observed. In the domain of the thin-layer cell, the thermodynamic properties of the anodic and cathodic peaks suggest non-ideal behaviour with interaction between active sites. Several methods were applied to measure the interaction parameters. Their values are negative, involving a repulsive energy of interaction. The effects of the pH on the film response are very important, being optimal at pH 3. At pH > 7, there is practically no response. However, the film is not destroyed and its response is recovered at pH 1. The effect of temperature on the peak current was also studied. The anomalies observed may be ascribed to the effect of temperature on the interaction parameters. On the other hand, kinetic effects were observed on the cathodic response of the film. Thus, E pc shifts with the sweep rate. This behaviour can be explained by assuming a chemical reaction coupled with the charge transfer. This kinetic effect depends on the temperature, and E pc shifts with T to more positive values, as expected. A redox mechanism of the polyoAP-modified film is proposed which involves addition-elimination of protons coupled to reversible one-electron transfer. The electrocatalytic properties of the polyoAP film electrode were tested for several typical substrates.