Electrodeposition and cycling of polypyrrole

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Abstract
Polypyrrole has been electrodeposited at a constant current density of 4 mA cm−2 onto Pt from 0.1 M pyrrole, 0.1 M NBu4 BF4 in dry CH3CN. The thickness of the polypyrrole has been varied over a wide range of 0.02 to 50 μm. Elemental analysis reveals an excess of hydrogen in the polymer. The electrochemical equivalent corresponds to an insertion of 25–35 mole % BF4‐anions and a current efficiency of 80–100% for the electrodeposition process. SEM technique shows a highly textured material at a thickness larger than 1 μm. Reversible water vapour adsorption of this material has been detected. The potential/time curve during galvanostatic electrodeposition is without special features. The start potential, USSCE = 0.9 V, is relatively negative. A slight decay of potential in the course of the electrodeposition of thick layers is explained in terms of increasing surface roughness. Cyclic voltammetry has been used for a systematic investigation into the role of the positive and negative endpotentials. The importance of a total primary discharge after electrodeposition has been clarified. At a film thickness d exceeding 1 μm, the cyclovoltammetric curve degenerates, and the anodic peak flattens and shifts to more positive potentials. Active mass utilization decreases with increasing d and with increasing voltage scan rate vs. The plot of anodic peak current density vs. vs is linear for layers below 1 μm thickness. For thick layers and at high vs, deviations occur, indicating a transport limitation in the film. As the film is not homogeneous, a quantitative evaluation is not possible.

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