Encapsulation of Fe/Fe3O4 in carbon nanotubes grown over carbon nanofibers for high performance supercapacitor electrodes

Abstract Carbon-based supercapacitive materials are promising energy storage materials because of their high power density and long durability. The energy density of carbon based materials can be significantly improved by making their hybrids with metal/metal oxides and hydroxides. Here, we successfully fabricated the electrospun carbon nanofibers (CNFs) with Fe encapsulated carbon nanotubes (CNTs) by simple chemical vapor deposition (CVD). The Fe nanoparticles later got oxidized by absorbing oxygen from air resulting in the desired hierarchical Fe/Fe3O4 encapsulated CNT/CNF nanostructure (Fe/Fe3O4@CNT-CNF). The composite material showed a high specific capacitance of 195 F g-1 at 0.5 A g-1, areal capacitance of 398 m F cm-2 in 1 M KOH and long term durability with 95% capacitance retention even after 5000 charge discharge cycles. The findings of our results suggest that Fe/Fe3O4@CNT-CNF hybrid is a potential candidate for electrode material of an electrochemical capacitor due to its distinctive nanoarchitectures and physiochemical properties.