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

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 alpha-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.