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 Ni-0 and OHads energy on NiO or NiOOH, the 3D electrode exhibits high performance in hydrogen evolution reaction with 146 mV at 10 mA cm(-2) and Tafel value of 72 mV dec(-1), and oxygen evolution reaction with 382 mV at 10 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 parallel to 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.