Asymmetric supercapacitor based on chemically coupled hybrid material of Fe₂O₃‐Fe₃O₄ heterostructure and nitrogen‐doped reduced graphene oxide

Abstract

The synthesis of a novel chemically coupled hybrid material based on Fe₂O₃-Fe₃O₄ heterostructure and nitrogen-doped reduced graphene oxide (N-rGO) for the development of high performance supercapacitor devices is demonstrated. The chemically coupled hybrid material is synthesized in a one-pot method under hydrothermal condition, resulting in the formation of crystalline α-Fe₂O₃ and poorly crystalline/amorphous Fe₃O₄. The Fe₂O₃-Fe₃O₄ particles have an average size of 30–50 nm. Chemical integration of Fe₂O₃-Fe₃O₄ with N-rGO through Fe-O−C bonds is achieved. The chemical coupling of N-rGO with pseudocapacitive Fe₂O₃-Fe₃O₄ enhances the overall performance of the composite. Two asymmetric supercapacitor devices using the hybrid material either as positive or negative electrode are fabricated. The supercapacitive behaviour is evaluated in terms of specific capacitance, energy density, power density and cycling stability, showing excellent performance. The asymmetric device based on hybrid material as the positive and activated carbon as the negative electrode, delivers a specific capacitance of 111.95 F g^-1 at 0.8 A g^-1 with an energy density of 44.93 Wh kg^-1. The supercapacitor has excellent cycling stability with a capacitance retention of >92% even after 10000 extensive charge-discharge cycles. The all-solid-state asymmetric supercapacitor device is fabricated using gel electrolyte. Solid-state devices connected in series successfully light up 29 LEDs.