In-situ fabricating MnO2 and its derived FeOOH nanostructures on mesoporous carbon towards high-performance asymmetric supercapacitor

Asymmetric supercapacitors with high energy density have received increasing attention in the past decade in order to meet the requirements of practical applications. The mesoporous carbon (SBA-C) with ordered parallel channels prepared using mesoporous silica as a hard template was wrapped with the ultrathin MnO2 nanosheets to construct a 3D hierarchical porous structure through a self-limiting reaction and the FeOOH nanoneedles were successfully derived by template-engaged redox etching using in-situ fabricating MnO2 nanosheet templates. The interesting hierarchical porous construction presents fast transfer paths of ions and electrons, good electrical conductivity, and high specific surface area. The as-fabricated nanohybrids exhibit high specific capacitance (219.7 F g−1 at 1 A g−1 of MnO2@SBA-C and 240.6 F g−1 at 2 A g−1 of FeOOH@SBA-C), good rate performance, and outstanding cycling stability. An asymmetric supercapacitor is assembled by using MnO2@SBA-C and FeOOH@SBA-C as the negative and positive electrode, which delivers a high energy density of 39.4 and 14.2 Wh kg−1 at a power density of 500 and 8000 W kg−1, respectively. The above satisfactory performance exhibits that in-situ fabricating MnO2 nanosheets and its derived FeOOH nanoneedles on mesoporous carbon present great potential to meet the energy/power characteristics of asymmetric supercapacitor in practical applications.