Cyclic voltammetry of polypyrrole in anhydrous acetonitrile

Abstract

Pyrrole was electrochemically polymerized in anhydrous acetonitrile with Et 4NClO 4 as the supporting electrolyte. Cyclic voltammetry was subsequently run in an anhydrous acetonitrile solution of Et 4NClO 4. Under such conditions it was found that only more deeply bound doping sites were involved, apparently due to H + ions released during polymerization. Consequently, the first reduction scan showed only one sharp peak at −0.56 V (versus SSCE). In the subsequent cycles of re-oxidation and reduction loosely bound doping sites were also involved leading to two observable peaks. The residual currents after the peak in the oxidation scan and before the peak in the reduction scan were not capacitive currents but faradaic currents. Water present in acetonitrile during polymerization made the counter anions in the polypyrrole (PPy) film more difficult to de-insert during the reduction scan. When LiClO 4 was used as the supporting electrolyte during polymerization, the PPy(ClO 4 −) obtained was found to be electrochemically inactive in an acetonitrile solution of Et 4NClO 4, but normal cyclic voltammograms could be obtained in an acetonitrile solution of LiClO 4. When cyclic voltammetry was run in LiClO 4 solution in acetonitrile for PPy(ClO 4 −) polymerized in acetonitrile with Et 4NClO 4 as the supporting electrolyte, the de-insertion of ClO 4 − was slow and incomplete during the reduction scan, so the de-insertion of ClO 4 − anions was accompanied by some insertion of Li + cations and, during the re-oxidation scan, Li + cations were de-inserted accompanying the re-insertion of ClO 4 −.