The morphology of NiCo2O4 can be controlled by changing the kinds of alkali source and the addition of NH4F, influencing its electrochemical properties.

We report a synthesis of NiCo2S4 nanosheet arrays with self-decorated nanoneedles on nickel foams by a facile and efficient two-step hydrothermal approach.We demonstrate that morphologies of various three-dimensional nanostructures such as nanoneedles arrays, nanosheet arrays, and nanoneedles-decorated nanosheet arrays can be manipulated by tuning the amount of the additive ammonium fluoride alone in the reaction. The unusual nanostructure of nanoneedles grown on surface of NiCo2S4 nanosheet arrays shows a large electroactive surface area and superior electrochemical properties. The electrode made of the NiCo2S4 nanosheet arrays with self-decorated nanoneedles shows greatly improved electrochemical performances with an ultrahigh specific capacitance of 2617.6 Fg −1 at a current density of 15 mAcm −2 and of 2051.0 Fg −1 even at a current density of 30 mAcm −2 . The electrode also exhibits an excellent cycling stability by retaining 93.2% of its original state after 5000 cycles, rendering the NiCo2S4 nanosheet arrays with self-decorated nanoneedles a potential electrode material for high-performance supercapacitors.

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