Synthesis of Polyaniline/Graphene Oxide Composites with Different Morphologies and Investigation of Their Electrochemical Properties

Polyaniline/graphene oxide composites of different morphologies were synthesized by oxidation polymerization method without using conventional oxidants. By changing the type of acid (doping agent) and its concentration, two different morphologies including worm-like morphology and flaky- or scalelike morphology were obtained. Morphology of these composites was studied by scanning electron microscopy (SEM). In order to achieve a better characterization of the polyaniline/graphene oxide composite, they were also investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). XRD analysis showed that, unlike in worm-like composite, crystallization was induced in flaky- or scale-like composite and the graphene oxide sheets were well exfoliated. To study electrochemical properties of the composites, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used. The synthesized polyaniline/graphene oxide composites were evaluated by measuring their electrochemical properties, and it was observed that only the worm-like composite was electrochemically active. The worm-like composite also showed a higher current density in the cyclic voltammetry test, due to its higher electrochemically active surface. Degree of conversion for composites was calculated and the kinetic data demonstrated that the composites were not polymerized completely, and therefore they did not show high electrochemical properties. The synthesized composites are suitable pre-polymers and their polymerization reaction can be completed by conventional oxidants, such as ammonium persulfate (APS) or by electrochemical method for high conversion of aniline monomer and improving the electrochemical properties of composite properties.