Pseudocapacitive behaviour of iron oxides supported on carbon nanofibers as a composite electrode material for aqueous-based supercapacitors

Abstract Due to the pseudocapacitive charge storage, transition metal oxides occupy a prominent position as high-energy-density electrode materials for supercapacitors. Environmentally friendly, facile synthesis and earth-abundant precursor materials are highly desirable in the investigation of novel electrodes. We report the synthesis of a binder-free electrode composed of iron oxide (FeOx) nanoparticles supported on radially oriented multi-walled carbon nanofibers (CNF). Characterization studies revealed a homogeneous distribution of nanoparticles composed of α-Fe2O3 (hematite), γ-Fe2O3 (maghemite), and Fe3O4 (magnetite) phases on the CNF scaffold. A high specific pseudocapacitance of 239.2 F g−1 was verified for the iron oxides due to contributions of the reversible solid-state redox reactions involving the Fe(II)/Fe(III) redox couple. Likewise, this work also discusses in detail the charge storage mechanism involving the FeOx species. It is reported a facile synthesis of an electrode material with a pseudocapacitive behaviour, good cyclability, and low equivalent series resistance (e.g., 3.79 mΩ g). As seen, the composite electrode material is promising for the energy storage process in aqueous-based supercapacitors.