Electrochemical supercapacitor and water splitting electrocatalysis applications of self-grown amorphous Ni(OH)2 nanosponge-balls

A promising self-growth (caused by surface modification due to oxidation/reduction) approach for the synthesis of nickel hydroxide (Ni(OH)2) nanosponge-balls on Ni-foam (NiF) electrode surface as a multifunctional electrode material for applications like energy storage and electrocatalysis is explored. Extensive physical and chemical characterizations carried out through advanced analytical techniques reveal the distinctive nanosponge-ball-type surface morphology of the Ni(OH)2@NiF, confirming the successful hydroxilation of the NiF electrode surface to Ni(OH)2@NiF. In terms of energy storage, on using Ni(OH)2@NiF electrode as a half-cell electrode material, an impressive specific capacitance of 803.08 F.g-1 at a current density of 6 mA.cm-2 is obtained, highlighting its energy storage potentiality. When integrated it into an asymmetric supercapacitor (ASC) alongside Bi2O3@NiF through the Ni(OH)2@NiF//Bi2O3@NiF, a remarkable power density of 2250 Wkg-1 at an energy density of 96.5 Wh kg-1 with exceptional cycling stability of 83.33 % even after 3500 cycles is confirmed. Moreover, on using the Ni(OH)2@NiF electrode as electrocatalyst, a robust activity with ultra-low overpotentials of 240 mV and 158 mV and Tafel slopes 62 mV dec-1 and 127 mV dec-1 are obtained for the oxygen evolution reaction and the hydrogen evolution reaction activities in a 6 M KOH electrolyte solution at a current density of 10 mA cm-2, respectively, suggesting importance of the developed Ni(OH)2@NiF electrode material in both energy storage and water splitting, into hydrogen and oxygen, applications.