Overoxidation of Polypyrrole in Propylene Carbonate: An In Situ FTIR Study

Irreversible oxidation of thin polypyrrole layers was studied in carbonate (PC) by the subtractively normalized interfacial Fourier transform infrared spectroscopy method. For comparison, some measurements were performed in acetonitrile instead of PC. In PC, carbon dioxide, a product of anodic oxidation of propylene carbonate, reacts with trace water present in the electrolyte to give . Nucleophilic and OH− species then attack the doped polypyrrole chains leaving a yellow, nonconjugated, and electrochemically rather inactive overoxidized polymer. The rate of overoxidation during polymer cycling in the 2.0–4.0 V (vs. Li/Li+) potential range depends strongly on the concentration of water in the electrolyte.