Composites of hierarchical metal–organic framework derived nitrogen-doped porous carbon and interpenetrating 3D hollow carbon spheres from lotus pollen for high-performance supercapacitors

Abstract

Composites (HPNCs/CS) of hierarchical metal–organic framework derived nitrogen-doped porous carbon (HPNC) and interpenetrating 3D hollow carbon spheres (CS) from lotus pollen are prepared via facile carbonization of Zn-metal–organic frameworks (ZIF-8) by controlling the appropriate temperature. In comparison with a single 3D hollow carbon sphere from lotus pollen, HPNCs/CS reduce the agglomeration of HPNCs and increase the specific surface area, and also promote electrical conductivity. In this work, HPNCs/CS materials exhibit high electrochemical performances with a high specific capacitance of 280 F g⁻¹ in 6 M KOH electrolyte at a current density of 1 A g⁻¹. Moreover, the symmetric supercapacitor (HPNCs/CS//HPNCs/CS) exhibits a special energy density of about 16.2 W h kg⁻¹ at a power density of 0.45 kW kg⁻¹ in a wide voltage region of 0–1.8 V and a superb cycle stability (89.0% capacitance retention after 10 000 cycles) at 0.5 A g⁻¹. Such marked response in electrochemical behaviors shows that the HPNCs/CS//HPNCs/CS supercapacitor is a promising practical energy-storage material.