Tetsubo-like α-Fe2O3/C nanoarrays on carbon cloth as negative electrode for high-performance asymmetric supercapacitors

Abstract To explore novel negative electrode materials with high special capacitance for high-performance asymmetric supercapacitors, in this article, α-Fe2O3/C nanoarrays on carbon cloth with tetsubo-like structure was synthesized as a free-standing negative electrode for supercapacitor. The characterizations indicated that these α-Fe2O3/C nanoarrays are hollow structure and composed of α-Fe2O3 nanocrystals and carbon nanoparticles. In addition, there are plenty of mesopores existed between these α-Fe2O3 nanocrystals and carbon nanoparticles. Due to the hollow porous structure of α-Fe2O3/C nanoarrays and the presence of carbon nanoparticles not only in favor of accelerating the transport of electron and ion in α-Fe2O3/C electrode, but also increasing the active sites for energy storage, the as-synthesized α-Fe2O3/C electrode delivered much enhanced electrochemical performance including a high specific capacitance up to 430.8 mF cm−2 and 391.8 F g−1 at a current density of 1 mA cm−2, good rate capability with a capacitance retention of 73.2% of capacitance retention at 10 mA cm−2 and great cycling stability with only 8.2% capacitance loss after 4000 cycles at a scan rate of 200 mV s−1. By using α-Fe2O3/C as negative electrode and MnO2 as positive electrode, an asymmetric supercapacitor was assembled to examine the electrochemical performance of α-Fe2O3/C in-depth. Benefit from the unique design of the α-Fe2O3/C electrode, the asymmetric supercapacitor exhibited a high energy density of 0.64 mWh cm−3 at the power density of 14.8 mW cm−3 in 1 M Na2SO4 electrolyte and 0.56 mWh cm−3 at the power density of 16.8 mW cm−3 in Na2SO4/CMC gel electrolyte. These satisfactory results prompt the as-fabricated hollow porous α-Fe2O3/C to use as a promising negative electrode material for high-performance supercapacitors.