Influence of copper anion complexes on the incorporation of metal particles in polyaniline. Part I: Copper citrate complex

Abstract

Copper electrodeposition in polyaniline-coated electrodes is studied using copper citrate complex anions as reducing species. Use of these complex anions allows shifting the potential window for metal deposition in the negative direction and resolving the polymer and metal reduction processes. As shown by galvanostatic experiments and SEM photographs, copper electrodeposition from citrate solution is highly inhibited and results in a small number (3.6 × 106 cm−2) of large hemispherical crystals located mainly on top of the polymer layer. Statistical analysis of distances between neighbouring crystals shows a random surface distribution of the copper hemispheres. Thus, the low number of crystals obtained cannot be related to the appearance and overlap of nucleation exclusion zones partly blocking the electrode surface. It is likely connected to the specific role of the metal anion complexes in the deposition process and more precisely to the inhibited diffusion of both the copper complex anions and the released (after reduction) citrate anions in and out of the polymer structure.