Asymmetric Supercapacitors Using Porous Carbons and Iron Oxide Electrodes Derived from a Single Fe Metal-Organic Framework (MIL-100 (Fe))

Abstract

MOF-derived carbon (MDC) and metal oxide (MDMO) are superior materials for supercapacitor electrodes due to their high specific capacitances, which can be attributed to their high porosity, specific surface area (SSA), and pore volume. To improve the electrochemical performance, the environmentally friendly and industrially producible MIL-100 (Fe) was prepared using three different Fe sources through hydrothermal synthesis. MDC-A with micro- and mesopores and MDC-B with micropores were synthesized through carbonization and an HCl washing process, and MDMO (α-Fe2O3) was obtained by a simple sintering in air. The electrochemical properties in a three-electrode system using a 6 M KOH electrolyte were investigated. These novel MDC and MDMO were applied to an asymmetric supercapacitor (ASC) system to overcome the disadvantages of traditional supercapacitors, enhancing energy density, power density, and cyclic performance. High SSA materials (MDC-A nitrate and MDMO iron) were selected for negative and positive electrode material to fabricate ASC with KOH/PVP gel electrolyte. As-fabricated ASC resulted in high specific capacitance 127.4 Fg−1 at 0.1 Ag−1 and 48.0 Fg−1 at 3 Ag−1, respectively, and delivered superior energy density (25.5 Wh/kg) at a power density 60 W/kg. The charging/discharging cycling test was also conducted, indicating 90.1% stability after 5000 cycles. These results indicate that ASC with MDC and MDMO derived from MIL-100 (Fe) has promising potential in high-performance energy storage devices.