▎ 摘　　要

The facile, single-step hydrothermal growth of Co9S8 on the surface of Ti3C2Tx (MXene)-/amine-functionalized graphene (NH2-RGO) was investigated as an ultrastable electrode material for both asymmetric and symmetric supercapacitor devices. The Ti3C2Tx/NH2-RGO sandwiched structure enhanced the conductivity by preventing agglomeration of MXene sheets. Furthermore, Co9S8 plays an important role to enhance the active metal ion sites over Ti3C2Tx/NH2-RGO nanosheets. The ratio of Ti3C2Tx/NH2 RGO to Co9S8 was optimized with a specific capacitance (801.3 F g (-1)) at 1 A g(-1) via a three-electrode setup of electrochemical analysis. The asymmetric device assembled using the optimum composite as cathode material delivered a maximum specific capacitance of 123.2 F g(-1) and energy density of 43.8 Wh kg(-1) as well as ultrahigh specific capacitance retention of 96.8% after 10 000 cycles. Furthermore, the asymmetric device was capable of lighting up white LEDs and powering up a 2 V fan. These results can effectively demonstrate the practical applicability of the MXene-based hybrid nanocomposite in energy industry.