Constructing Fe₂O₃/Carbon heterointerfaces on porous carbon fibers: Achieving a synergistic effect for enhanced supercapacitors

Nanocomposites consisting of metal oxide and carbon materials are usually preferred as electrode for electrochemical energy storage. Nonetheless, their unsatisfied capacitance hinders the reached energy density of aqueous supercapacitors (SCs). Herein, Fe 2 O 3 /carbon heterointerface was constructed on porous carbon fiber (PCF), which could serve as an efficient active site for stabilizing K + and Na + storage. The theoretical calculations revealed the enhanced accumulation and transfer of charges around the Fe 2 O 3 /carbon interface, thus favoring the electron transfer and boosting the faradaic reaction. The interactions of Fe 2 O 3 and PCF was found to simultaneously cause faster ion transfer and more surface charge storage, which made the as-prepared Fe 2 O 3 @PCF electrode deliver a superior SCs performance in 2 M KCl or 1 M Na 2 SO 4 electrolyte. The asymmetric aqueous supercapacitor devices consisted of Fe 2 O 3 @PCF and MnO 2 /CC electrodes with maximum operating potential of 2.0 V achieved a high areal energy density of 0.126 mWh cm −2  at a power density of 1.2 mW cm −2 along with good stability.