Graphene/Polyaniline Nanofiber Composites as Supercapacitor Electrodes

TLDR

The authors synthesized graphene/PANI nanofiber composites by in situ polymerization of aniline on graphene oxide, followed by reduction, reoxidation, and reprotonation, and characterized the resulting materials with XRD, NMR, FT‑IR, SEM, TEM, TGA, and XPS. The uniform graphene/PANI nanocomposite exhibited high conductivity and delivered a specific capacitance of 480 F g⁻¹ at 0.1 A g⁻¹ with excellent cycling stability, demonstrating that either PANI‑doped graphene or graphene‑doped PANI can achieve high performance.

Abstract

Chemically modified graphene and polyaniline (PANI) nanofiber composites were prepared by in situ polymerization of aniline monomer in the presence of graphene oxide under acid conditions. The obtained graphene oxide/PANI composites with different mass ratios were reduced to graphene using hydrazine followed by reoxidation and reprotonation of the reduced PANI to give the graphene/PANI nanocomposites. The morphology, composition, and electronic structure of the composites together with pure polyaniline fibers (PANI-F), graphene oxide (GO), and graphene (GR) were characterized using X-ray diffraction (XRD), solid-state 13C NMR, FT-IR, scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). It was found that the chemically modified graphene and the PANI nanofibers formed a uniform nanocomposite with the PANI fibers absorbed on the graphene surface and/or filled between the graphene sheets. Such uniform structure together with the observed high conductivities afforded high specific capacitance and good cycling stability during the charge−discharge process when used as supercapacitor electrodes. A specific capacitance of as high as 480 F/g at a current density of 0.1 A/g was achieved over a PANI-doped graphene composite. The research data revealed that high specific capacitance and good cycling stability can be achieved either by doping chemically modified graphenes with PANI or by doping the bulky PANIs with graphene/graphene oxide.