Electrosynthesis of polypyrrole in iodide solution. Film growth, redox behaviour and potentiometric response

Electrosynthesis of polypyrrole (PPy) was studied in aqueous lithium iodide solution. The electrochemical polymerization showed features of two-dimensional growth and the reaction was catalyzed by the I2/I− couple. The potentiometric response of PPy doped with iodide (PPy(I)) was studied both in iodide solutions and solutions containing the redox couple I2/I− with a fixed concentration ratio 0.4 but varying the initial concentration of iodide in the range 10−5–1.0 M. Linear, anionic response was observed in the concentration range 10−1–10−3 M when only iodide species was present. However, contribution of the redox response to the overall potentiometric response increased with increasing concentration of I2 although the concentration ration between iodine/iodide was kept constant. The influence of phosphate buffer on the electroactivity of PPy doped with iodide was also studied.