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

The electrochemical generation of graphene-polypyrrole composite films is presented here using pristine, oxide-free graphene flakes obtained by 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 overoxidation-degradation processes, were determined from the voltammetric responses of the different solutions. Then, a parallel study of the electrogeneration of FMN-G-PPy films on clean Pt electrodes using cyclic voltammetry, potentiostatic or galvanostatic conditions was performed. The subsequent electrochemical characterization of the resulting films and a parallel energy-dispersive X-ray spectroscopy analysis of different oxidized states reveal a separate oxidation/reduction of graphene and polypyrrole inside the material. Graphene reactions (n-doping) drive the exchange of cations while 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 scanning electron microscopy.