Ni@NiO Nanowires on Nickel Foam Prepared via "Acid Hungry" Strategy: High Supercapacitor Performance and Robust Electrocatalysts for Water Splitting Reaction.

Ni/NiO core-shell nanowires on nickel foam (NF) are successfully synthesized using an "acid-hungry" strategy. The 3D electrode with large accessible active sites and improved conductivity, possesses an optimized ionic and electronic transport path during electrochemical processes. High areal capacitance of 1.65 F cm-2 is obtained at an ultrahigh current density of 100 mA cm-2 , which is 19.88 times higher than pristine NF. The direct growth of nanowires makes the present supercapacitor electrode robust for long-term cycling test. By virtue of the favorable hydrogen adsorption energies on Ni0 and OHads energy on NiO or NiOOH, the 3D electrode exhibits high performance in hydrogen evolution reaction with 146 mV at η10 mA cm-2 and Tafel value of 72 mV dec-1 , and oxygen evolution reaction with 382 mV at η10 mA cm-2 and Tafel value of 103 mV dec-1 in 1 m KOH. An electrolyzer using 3D electrodes as both anode and cathode can yield a current density of 10 mA cm-2 at 1.71 V, and possesses superior long-term stability to an electrolyzer consisting of Pt/C||Ir/C. The present work develops an effective and low-cost method for the large-scale fabrication of Ni/NiO core-shell nanowires on commercial NF, providing a promising candidate for supercapacitors, fuel cells, and electrocatalysis.