Electrochemical performance of nickel hydroxide nanopetals for supercapacitor electrodes

•Chemically precipitated Ni(OH)2 over graphite foil as supercapacitor electrode.•Demonstrated laudable specific capacitance of 701 F g−1 at 1 Ag−1.•Favourable capacitance retention of 84.16% achieved even after 5000 redox cycles.•Unrestricted ion movement on electrode surface increased charge storage capability. Nickel hydroxide and nickel oxide were prepared via a facile chemical precipitation method, whose structure, morphology and electrochemical properties were compared. Nickel hydroxide demonstrated nanopetal-like morphology, pseudocapacitive nature, a superior specific capacitance of 701 F g−1 at 1 A g−1 and admirable capacitance retention of 84.16% even after 5000 consecutive charge–discharge cycles in 2 M KOH aqueous electrolyte. Meanwhile, nickel oxide grew into a cluster of randomly shaped nanostructures with pseudocapacitive behavior and comparatively lower specific capacitance of 171 F g−1 at 1 A g−1. In nickel hydroxide, the freedom of movement of electrolyte ions is responsible for its loftier charge storage capability.