Sulphur source-inspired self-grown polycrystalline and mesoporous nickel sulfide (Ni xS y) superstructures with vertically aligned nanomorphologies viz. rods, flakes, buds, and petals, synthesized at elevated temperatures and moderate pressures by a facile one-pot hydrothermal method on a three-dimensional Ni foam demonstrate remarkable areal specific capacitances of 7152, 4835, and 2160 F cm-2 at current densities of 1, 2, and 5 mA cm-2, respectively, with a cycling stability of 94% for a battery-type electrochemical supercapacitor when used as an electrode material in a supercapacitor. The Ni xS y//Bi2O3 asymmetric supercapacitor assembly exhibits an energy density of 41 W h·kg-1 at a power density of 1399 W kg-1 for 1 A g-1 and was used in a three-cell series combination to operate a "GFHIM" display panel (our research institute name, Global Frontier R & D Center for Hybrid Interface Materials) composed of nearly 50 differently colored light-emitting diodes with high intensity in 1 M KOH water-alkali electrolyte. The electrochemical supercapacitor results obtained for the Ni xS y superstructures because of a combination of catalytically active amorphous and high mobility polycrystalline are highly comparable to those reported previously for salt-mediated and self-grown Ni xS y structures and morphologies.
Keywords: electrochemical supercapacitors; hydrothermal synthesis; morphology evolution; self-grown NixSy superstructures; structural elucidation.