ELECTRODE-POTENTIALS OF ELECTRONICALLY CONDUCTING POLYMER POLYPYRROLE

The electrode potentials of electronically conducting polymer polypyrrole film-coated Pt electrodes (PPy/Pt) and the effects of the solution pH, electrolyte concentration, temperature, and spontaneous counter anion exchange on the potentials have been studied. The results indicate that the electrode potentials are the genuine responses of the polymeric coating. Thus measurement of the potentials provides a novel method to investigate the conducting polymer which is usually intractable. PPy/Pt electrodes definitely respond to the pH value of an electrolyte solution in contact but do so quite slowly, due to the slow protonation and deprotonation involved in PPy. The potential-pH diagram shows an inclined line with a slope around -40 mV/pH, depending slightly on the PPy layer thickness. The electrodes are very sensitive to the change of the electrolyte concentration. The slope values of the potential-logC lines are related to the solution pH. Nernst response is observed in solutions at ca pH 7, indicative of the use of such electrodes as ion sensors.