Electrochemical Synthesis and Characterization of Flavin Mononucleotide-Exfoliated Pristine Graphene/Polypyrrole Composites.

The electrochemical generation of graphene-polypyrrole composite films is presented here by using pristine, oxide-free graphene flakes obtained through the direct exfoliation of graphite in water with flavin mononucleotide (FMN) as a colloidal stabilizer (FMN−G-PPy films): an environmentally friendly methodology. The best potential and current ranges for the electropolymerization of pyrrole in the presence of FMN−G, trying to avoid parallel over-oxidation/degradation processes, were determined from voltammetric responses of the different solutions. Then, a parallel study of the electrogeneration of FMN−G-PPy films on clean Pt electrodes by using cyclic voltammetry, potentiostatic or galvanostatic conditions, was performed. The subsequent electrochemical characterization of the resulting films and parallel energy-dispersive X-ray spectroscopy analysis of different oxidized states revealed the separate oxidation/reduction of graphene and polypyrrole inside the material. Graphene reactions (n-doping) drive the exchange of cations, whereas polypyrrole reactions (p-doping) drive the exchange of anions. The specific charge storage in FMN−G-PPy, 207 mC mg⁻¹, is higher than that stored in polypyrrole, 141 mC mg⁻¹, indicating some synergy. An unexpected high content of anions was found in deeply reduced materials. The surface morphology of the oxidized and reduced materials generated by different methodologies was studied by using scanning electron microscopy. [ABSTRACT FROM AUTHOR]