Boosting the performance of supercapacitors based hierarchically porous carbon from natural Juncus effuses by incorporation of MnO2

Porous carbons have recently drawn extensive attention in energy conversion and storage devices. Boosting energy densities of carbon family is still a challenge due to their limited surface area and accessible active sites. In this work, porous carbons with hierarchically structures were prepared from natural Juncus effuses (CJE) and homogeneous MnO2 layer was successfully incorporated on their surfaces without changing their original porous structure. The CJE/MnO2 composite showed large specific capacitance (283 F/g at 1 A/g), which was on account of high specific surface area (1283 m(2)/g) and abundant active sites for pseudocapacitance, particularly, resulted from the introduction of MnO2. Significantly, the assembled symmetric supercapacitor from CJE/MnO2 in Na2SO4 aqueous electrolyte delivered high energy/power densities (19.13 Wh/kg at 225 W/kg and 13.73 Wh/kg at 8984 W/kg) and good cyclic performance (86.2% capacitance retention over 5000 cycles at 10.0 A/g). These results demonstrate the CJE/MnO2 composite can be a potential candidate for supercapacitors. (C) 2019 Elsevier B.V. All rights reserved.