MOF-derived porous Ni₃S₄/CoS nanosheet arrays for flexible supercapacitor electrode

Metal organic framework (MOF) is the preferred template for the preparation of porous nanostructures; we have synthesized Ni3S4/CoS nanosheet arrays in situ on carbon fiber based on MOF-Co. The synthesis process involves simple MOF-Co nanoarray growth, ion exchange/etching, and sulfurization reaction. The as-prepared Ni3S4/CoS shows porous nanosheet structure, and it can be served as a binder-free supercapacitor electrode. The cyclic voltammogram curves and galvanostatic charge-discharge curves of Ni3S4/CoS electrode display typical pseudocapacitive behaviors. The calculated areal capacitance of Ni3S4/CoS electrode is 5.1 F cm(-2) under the current density of 2 mA cm(-2), which is distinctly larger than that of bare CoS electrode. The long-term cycling measurement reveals that Ni3S4/CoS electrode has excellent cycling stability, maintaining 98.3% capacitance retention under 6 mA cm(-2) after 5000 cycles. The related mechanisms for the optimized electrochemical performance are discussed according to the synergistic effect, porous nanostructure, and the conductivity. These results facilitate the potential realization of sulfide nanocomposites in high-performance supercapacitors.