Electrochemical Synthesis and Characterization of 1,2-Naphthaquinone-4-Sulfonic Acid Doped Polypyrrole

Abstract

Polypyrrole thin film microelectrodes prepared from an aqueous solution of the sodium salt of 1, 2-napthaquinone-4-sulfonic acid and pyrrole in hydrochloric acid as the supporting electrolyte was characterized electrochemically for the first time and found to exhibit good electronic and spectroscopic properties. Voltammetric investigations showed that the polymer exhibited quasireversible kinetics in a potential window of -400 mV to 700 mV, with a formal potential of 322 mV vs. Ag/AgCl. The diffusion coefficient was calculated to be 1.02×10-6 cm2 s-1 for a thin film with a surface concentration of 1.83×10-7 mol cm-2 having a rate constant of 2.20×10-3 cm s-1 at 5 mV s-1. Electrochemical impedance spectroscopy provided quantitative information about the conductivity changes within the modified polymer and support for the quasireversible kinetics suggested by voltammetry. The changes in electrical properties of the polymer during electrochemical p-doping and n-doping were quantified by equivalent electrical circuit fitting and assisted in the identification of the suggested kinetic mechanism. SNIFTIRS confirmed the incorporation of the surfactant into the polypyrrole film and for the first time structural changes within the polymer were observed that could be related to the observed electrochemistry of the polymer.