Polypyrrole-encapsulated Fe2O3 nanotube arrays on a carbon cloth support: Achieving synergistic effect for enhanced supercapacitor performance

Abstract It is highly attractive to design Fe2O3-based nanocomposite anodes for supercapacitors (SCs). Herein, polypyrrole-encapsulated Fe2O3 nanotube arrays grown on carbon cloth (Fe2O3 NTs@PPy/CC) were fabricated by combination of sacrificial template and electrodeposition methods. Such Fe2O3 NTs@PPy/CC exhibits boosted pseudocapacitance and stability. In 1 M Na2SO4, it delivers a specific capacitance of 237 mF cm−2 at 1 mA cm−2, and still retains 80% of initial capacity at 10 mA cm−2 even after 10,000 cycles. The theoretical calculation results reveal that PPy exhibits a strong adhesion on the surface of Fe2O3, and then effectively stabilizes the electrode structure. The interface between Fe2O3 and PPy possesses more stable Na+ storage sites to substantially enhance pseudocapacitance. The interactions of Fe2O3 nanotube arrays and conductive polymers can simultaneously cause faster ion transfer, more surface charge storage, and higher structural stability for Fe2O3. The asymmetric aqueous supercapacitor devices consisted of Fe2O3 NTs@PPy and MnO2 electrodes with maximum operating potential of 2.0 V achieve a high areal energy density of 59.4 µWh cm−2 (24.2 Wh kg−1) at a power density of 1 mWh cm−2 (408.2 W kg−1) along with good stability. This work seeks a deeper insight for synergistic effect between PPy and Fe2O3, and offers a novel strategy to design the nanostructured composite with enhanced interface area for energy storage.