An Impedance Study about the Effect of pH on the Electron Transport Rate at Poly(o-aminophenol) Film Electrodes

Impedance measurements on poly(o-aminophenol) (POAP) film electrodes in solutions of different pH were carried out. Impedance spectra were interpreted in terms of the modified electron hopping model described in F.J. Rodríguez Nieto, R. Tucceri, J. Electroanal. Chem., 416(1996), 1. An increase of the metal/POAP interfacial resistance with an increase of pH was obtained. With regard to the bulk charge-transport process, a decrease in the electron diffusion coefficient with an increase of pH was extracted from the fitting procedure. The change of the charge-transport and charge-transfer parameters with the increase in pH was attributed to an increase in the electron hopping distance between adjacent redox sites in POAP films. Impedance results are in agreement with potentiodynamic surface resistance measurements carried out in [10].