Nanocomposites of graphene materials and conducting polymers have been extensively studied as promising materials for electrodes of supercapacitors. Here, we present a graphene/polyaniline heterostructure consisting of a CVD-graphene and polyaniline monolayer and its electrochemical operation in a supercapacitor. The synthesis employs functionalization of graphene by p-phenylene sulfonic groups and oxidative polymerization of anilinium by ammonium persulfate under reaction conditions, providing no bulk polyaniline. Scanning electron microscopy, atomic force microscopy, and Raman spectroscopy showed the selective formation of polyaniline on the graphene. In situ Raman spectroelectrochemistry and cyclic voltammetry (both in a microdroplet setup) confirm the reversibility of polyaniline redox transitions and graphene electrochemical doping. After an increase within the initial 200 cycles due to the formation of benzoquinone-hydroquinone defects in polyaniline, the specific areal capacitance remained for 2400 cycles with ±1% retention at 21.2 μF cm-2, one order of magnitude higher than the capacitance of pristine graphene.
Keywords: CVD-graphene; Raman spectroelectrochemistry; polyaniline monolayer; supercapacitor; two-dimensional heterostructure.