Hydrothermal synthesis and pseudocapacitive properties of morphology-tuned nickel sulfide (NiS) nanostructures

Metal sulfides have attracted considerable scrutiny compared to metal oxides owing to their distinguished electrochemical properties and various applications, such as solar cells and supercapacitors. We have reported the pseudocapacitive properties of morphology-tuned NiS nanostructures using a hydrothermal method at different deposition times and temperatures. The surface morphology, structure, and chemical composition have been confirmed by SEM, TEM, XRD, XPS and EDS analyses. The optimized NiS-2 h electrode offers extra conductive paths on nickel foam, yielding a lower charge-transfer resistance and internal resistance than those of NiS-1 h and NiS-3 h. An investigation of its electrochemical properties indicates that the NiS electrode exhibited a specific capacitance of 1073.8 F g(-1) and 959 F g(-1) at current densities of 1.2 and 2.4 A g(-1) in KOH solution, indicating its potential to be used in practical applications. Moreover, it delivered a maximum energy density of 23.19 W h kg(-1) and a power density of 243.9 W kg(-1) with an excellent cycling retention of 89% after 1000 charge-discharge cycles. This work also indicates an effective approach for the fabrication of high-performance electrodes in a cost-effective manner for higher energy density and power density applications, such as electric vehicles, flexible electronics, and energy storage devices.