Nucleation and Growth Kinetics of Electrodeposited Sulfate-Doped Polypyrrole: Determination of the Diffusion Coefficient of SO₄²⁻ in the Polymeric Membrane

Abstract

A kinetic study for the electrosynthesis of polypyrrole (Ppy) doped with SO(4)(2-) ions is presented. Ppy films were electrochemically polymerized onto a graphite-epoxy resin electrode. Experimental current density transients (j-t) were obtained for three different potentiometric behaviors: anionic, cationic, and a combination. Theoretical models were used to fit the experimental j-t data to determine the nucleation and growth processes controlling the polymer synthesis. It was encountered that, in all cases, pyrrole electropolimerization involves two concomitant processes, namely, a Ppy diffusion limited multiple 3D nucleation and growth and pyrrole electro-oxidation on the growing surface of the Ppy nuclei. SEM analysis of the electrodes surfaces reveals that Ppy deposition occurred over most of the electrode surface by multiple nucleation of hemispheres, as the theoretical model used for the analysis of the current transients required. Hemispherical particles formed the polymeric film displaying different sizes. The order for the particle size was as follows: anionic > anionic-cationic > cationic. These results are congruent with those obtained by theoretical analysis of the corresponding current transients. Analysis of the impedance measurements recorded on the anionic Ppy film, immersed in an aqueous solution with different sulfate ion concentrations evidenced that SO(4)(2-) ions diffuse through the Ppy film provoking a decrease of its electrical resistance and an increase of its dielectric constant. From the Warburg impedance coefficient, the sulfate coefficient of diffusion in the Ppy film was 1.38 x 10(-9) cm(2) s(-1).

Electrochemical supercapacitive properties of polypyrrole thin films: influence of the electropolymerization methods

“…According to Licona-Sanchez et al, the shape of PPy electrode position curve from PS synthesis (Fig. 1c) can be explained by the superposition of two simultaneous processes that occur at the electrode surface, namely, multiple 3D hemispherical nucleation, and growth, where oxidation of pyrrole takes place on fresh PPy surface [21]. The electropolymerization mechanism of PPy thin films is schematically illustrated in Fig.…”

The importance of the film structure during self-powered ibuprofen salicylate drug release from polypyrrole electrodeposited on AZ31 Mg

“…In addition, the incorporation of IBU into the polymer structure, either as a dopant or inclusion, also limits the growth processes of the polymer likely due to steric effects. IBU is a large molecule in comparison with other counter ions, such as Cl − or ClO 4 − used to balance the charge during the polymerization and changes nucleation and growth processes [21,26,27]. SEM micrographs of PPy films prepared in SA-Py and SAPy-0.5IBU solutions are shown in Fig.…”

High‐lateral resolution X‐ray fluorescence microspectroscopy and dynamic mathematical modelling as tools for the study of electrodeposited electrocatalysts

“…[77] Eventually, regarding PPy electrodeposition, N&G has been demonstrated to be very similar to that of metals, and the same models have been used as for metal Electrodeposition. [74,78] As far as the numerical simulation with our model is concerned, the instantaneous area of the surface defined by the shape function Eqn (A1), corrected for diffusion (e.g. with a Cottrell 1/√t coefficient) if required, is directly proportional to the current transient corresponding to classical potentiostatic nucleation experiment, as described earlier in the present section.…”