Metal-organic framework derived Co9S8/Ni3S2 composites on Ni foam with enhanced electrochemical performance by one-step sulfuration strategy for supercapacitors electrode

Abstract

Electrode materials with excellent performance are urgently demanded for supercapacitors. Herein, heterogeneous nanostructure Co9S8/Ni3S2 supported on conductive Ni foam (Co9S8/Ni3S2/NF) is fabricated using zeolite imidazole frameworks (ZIFs) as the sacrificial template. The Co9S8/Ni3S2/NF electrode shows an outstanding specific capacitance of 1356 F g−1 at a current density of 1 A g−1 and still remained 1145 F g−1 at 10 A g−1. The enhanced electrochemical performance should be attributed to the superior structural characteristics, the abundant active sites, the rich redox reactions, the strongly synergistic effect in heterogeneous sulfide composition and the good conductivity resulted from the NF and the Co9S8/Ni3S2/NF. Meanwhile, to further evaluate the practical application value of the Co9S8/Ni3S2/NF electrode, a hybrid supercapacitors (HSCs) device is constructed using Co9S8/Ni3S2/NF as positive electrode and activated carbon (AC) as negative electrode, and it displays a high energy density of 48.2 Wh kg−1 at a power density of 799.6 W kg−1 and a superior long-term cycling stability with 82% of initial capacitance after 8000 cycles. In addition, two as-assembled capacitors in series can light 7 LED bulbs. This strategy of obtaining multi-metal sulfides from Co/Ni-ZIF precursor provides a new perspective to design and develop electrode materials for high-performance hybrid supercapacitors.