Hierarchical assembly of graphene/polyaniline nanostructures to synthesize free-standing supercapacitor electrode

Free-standing composite films based on graphene/polyaniline (PANI) nanostructure were synthesized for supercapacitor application. First, polyaniline nanospheres were prepared by microemulsion polymerization, followed by the incorporation of graphene oxide nanosheets by hierarchical organization. The cationic PANI nanospheres were attached to the anionic GO sheets by electrostatic interaction and hierarchical deposition of GO/PANI nanostructures on a membrane filter via targeted self-assembly. Subsequent in situ chemical reduction of GO using hydroiodic acid produced well-defined graphene/PANI nanostructures having interpenetrating network with 3D open structure. The in situ GO reduction enabled keeping the hierarchical organization intact. The flexible graphene/PANI film produced was tested as a supercapacitor electrode using voltammograms and Nyquist analysis. The electro-capacitance of the film (448 F/g) was enhanced by 60% through the synergistic combination of graphene and PANI nanostructures. About 81% capacity retention was achieved for the composite compared to 38% for PANI alone after subjecting the samples to 5000 cyclic operations.