Nanostructured ternary composites of graphene/Fe2O3/polyaniline for high-performance supercapacitors

Abstract

Well-designed nanostructures of a ternary nanocomposite, graphene/Fe₂O₃/polyaniline, are fabricated via a two-step approach. Graphene oxide is reduced by Fe²⁺ and well-dispersed by loading α-Fe₂O₃ nanoparticles (20–70 nm in size). A thin film of polyaniline is in situ polymerized on the graphene/Fe₂O₃ surfaces for the fabrication of its ternary composite. Among the composites obtained at different ratios of graphene/Fe₂O₃ to polyaniline, the ternary graphene/Fe₂O₃/polyaniline with a ratio of 2 : 1 exhibits a high specific capacitance of 638 F g⁻¹ in 1 M KOH at a scan rate of 1 mV s⁻¹ and experiences only a negligible decay of 8% after 5000 cycles. It also shows a higher energy density at high power density than other ternary or binary composites of the three components, respectively. The extraordinary electrochemical performance of the composite arises from the well-designed structural advantages of the ternary nanocomposite, and the good combination and synergistic effects among the three components. Graphene sheets, as the conducting frameworks for sustaining polyaniline and Fe₂O₃, can separate and disperse well in the composite due to the existence of Fe₂O₃. On the other hand, the thin film of polyaniline on the surface of graphene/Fe₂O₃ not only enhances the surface area, but also restricts the dissolution, aggregation and volume changes of Fe₂O₃ during charge–discharge cycling. Additionally, the existence of Fe₂O₃ is helpful to increase the rate stability of the ternary composite. The ternary composites with synergistic effects can take advantage of both Faradaic and non-Faradaic processes for capacity-charge storage with excellent electrochemical properties.