Enhanced supercapacitive performance in Ni3S2/MnS composites via an ion-exchange process for supercapacitor applications

Mixed transition metal sulfides with high electrochemical activity and theoretical capacitance have been investigated as promising electroactive materials for energy-related applications. Herein, a series of Ni3S2/MnS (NMS) composites with different sulfurization times were directly grown on reduced graphene oxide (rGO)-coated Ni foam (NF) via a facile and cost-effective hydrothermal method (NMS/rGO). The time-dependent experiments show that the sulfurization time exhibits a pronounced influence on the morphologies and electrochemical properties of NMS/rGO composites. Remarkably, the optimum electrochemical performance was obtained in the composite when the sulfurization time is 3 h (NMS/ rGO-3h). The NMS/rGO-3h electrode exhibits a high specific capacitance of 3374.6 F g(-1) at a current density of 1 A g(-1) along with an outstanding cycling stability of 90.7% at 10 A g(-1) through 8000 suc-cessive cycles. Furthermore, an asymmetric supercapacitor composed of NMS/rGO-3h electrode as a positive electrode and nitrogen-rich rGO as a negative electrode was assembled, which provided a maximum energy density of 58.9 W h kg-1 at 852.3 W kg(-1) and a suitable cycling performance of 99% over 8000 cycles. The superior electrochemical behavior of NMS/rGO composites indicates their potential utilization as electrodes for energy conversion and storage devices. (C) 2020 Elsevier Ltd. All rights reserved.