Investigation of electrochemical degradation process in polyaniline/polystyrene sulfonated self-assembly films by impedance spectroscopy.

In this study, the electrochemical degradation of polyaniline/polystyrene sulfonated (PANI/PSS) self-assembly films was investigated by an electrochemical impedance technique using transmission line models to fit the results. The experiments were performed by polarizing the working electrode at a fixed oxidative potential of 0.55 V. The results showed that changes in the electrochemical behavior of the oxidized PANI/PSS film occurred mainly in the polymer/solution interface by an increase in the charge transfer resistance.

Investigation of polypyrrole degradation using electrochemical impedance spectroscopy.

In this paper, the electrochemical degradation of polypyrrole film was studied by means of overpotential application. The overpotential was 0.58 V versus SCE, and after every 5 min of application of 0.58 V, a cyclic voltammogram was recorded in the range of -0.7 to 0.5 V as well as an electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance (EIS and EQCM). The main characteristic is the huge increase in the charge transfer resistance (r(ct)), which indicates that the insertion process of ions in the polymer matrix is hindered by the electrochemical degradation. Once the process of insertion is damaged, the number of intercalated ions in the matrix should decrease, which is expressed by the low-frequency capacitance, which is proportional to the number of intercalated ions in the polymeric matrix. The decrease of intercalated ions has an influence in the mass variation of the polymer film, which is confirmed by EQCM measurements.

Development of low-cost metal oxide pH electrodes based on the polymeric precursor method.

In this work, the polymeric precursor method was used to prepare low-cost solid-state sensors for pH determination based on iridium oxide as the main pH sensitive material. The iridium content was reduced with addition of TiO(2), forming the binary system IrO(x)-TiO(2), whose electroanalytical properties were evaluated in comparison with a commercial glass pH electrode. The minimum iridium content which gave suitable results was 30mol%, and the electrode presented Nernstian and fast response in the pH range from 1 to 13, with no hysteresis effect observed. Besides, the electrode showed high selectivity in the presence of alkali ions as Li(+), Na(+) or K(+). The amount of iridium in the prepared electrodes was very small (<0.1mg), supporting the efficiency of this method on the simple preparation of functional low-cost pH electrodes.