Ion transport and degradation studies of a polyaniline-modified electrode using SECM

The morphology and ion transport characteristics of polyaniline (PANI) films on a platinum electrode were investigated using scanning electrochemical microscopy method (SECM). An ultramicroelectrode (UME) tip was positioned close to the surface of a PANI-modified substrate electrode, and the current signal at the tip and substrate electrodes, during a substrate potential step or linear sweep were monitored simultaneously. Proton transport occurred on the PANI film at a pH of 6 during the first and second redox cycles of PANI was monitored at this pH. The chemical reaction pathway of PANI as a function of substrate potential was analyzed. Different species of degradation products were detected electrochemically at the SECM tip. Benzoquinone (BQ) was found to be the major product of anodic degradation of PANI. Chemical imaging of the anodic degradation of PANI was performed by SECM during applying different potential steps to the PANI. The anodic threshold of 0.75 V was suggested as the potential at which degradation of PANI begins.