Effect of Prolonged Electrode Potential Cycling on the Charge Transport Parameters of Poly(o-aminophenol) (POAP) films

ARNAL, P.M. TUCCERI

Querétaro

Congreso; 64th Annual Meeting of the International Society of Electrochemistry; 2013

The aim of this work was to study the effect of prolonged potentiodynamic cycling on the conducting properties of poly(o-aminophenol) (POAP) film electrodes. Cyclic Voltammetry (CV), Surface Resistance (SR), Rotating Disc Electrode Voltammetry (RDEV) and Electrochemical Impedance Spectroscopy (EIS) were employed to study the change in the charge-transport parameters of POAP with potentiodynamic cycling within the potential range of maximal electroactivity of the polymer (-0.2 V < E < 0.5 V (SCE)). The attenuation of the voltammetric response of the polymer with the increase in the number of oxidation-reduction cycles allowed one to define a degree of deactivation. Also, the attenuation of the relative resistance changes (DR/R) of a gold film coated with a POAP film allowed one to propose that inactive zones develop within the redox sites configuration of the polymer after prolonged potentiodynamic cycling. RDEV and impedance measurements were employed to obtain dependences of charge-transport and charge-transfer parameters on the degree of deactivation of the polymer. RDEV data were interpreted on the basis of the electron hopping model. Impedance diagrams of POAP films in the sole presence of the supporting electrolyte and in the presence of an electroactive solution were analyzed on the basis of two different impedance models. While diffusion coefficients for electron (De) and ion (Di) transport decrease, interfacial resistances related to ion and electron transfer across the different interfaces involved in the metal/polymer film/solution system (Rm|f, Rif|s, Ref|s) increase as the degree of deactivation increases. The slower electron transport with the increase in the degree of deactivation was attributed to the increase of the electron hopping distance between redox sites, which is consistent with the attenuation of the surface resistance change caused by the presence of inactive sites in the redox site configuration of a deactivated film. Transport parameters, such as, polymer-solution interfacial ion-transfer resistance, Rif|s and Di, were associated with proton movements. While parameters representing electron motion extracted from RDEV and impedance measurements seem to change continuously within the whole range of deactivation degree, parameters representing ion transport show a break at a degree of deactivation of about 0.35. This effect could be related to the existence of two forms of hydrogen ions in the POAP film. In this work it is demonstrated that POAP films maintain their conducting properties almost unaltered for about 500 potential cycles at a scan rate of 0.010 V s-1. However, a loss of conductivity was observed as the number of potential cycles was extended beyond 500.