Heterostructured Ni(OH)₂/Ni₃S₂ Supported on Ni Foam as Highly Efficient and Durable\nBifunctional Electrodes for Overall Water Electrolysis

Abstract

Development of efficient,\nstable, and robust bifunctional electrodes is important for the practical\nand industrial application of water electrolysis technologies for\nrenewable hydrogen production. Here, we report the fabrication of\nheterostructured Ni­(OH)₂ nanosheets/Ni₃S₂ nanoneedles grown on Ni foam, Ni­(OH)₂/Ni₃S₂/NF, as a highly active and mechanically strong bifunctional\nelectrode for overall water splitting. The results indicate that heterostructured\nNi­(OH)₂/Ni₃S₂ interfaces are the\nreactive center for the oxygen evolution reaction (OER) and hydrogen\nevolution reaction (HER). The redistribution of electrons and formation\nof the Ni^δ+ and S^δ− active\nspecies serve as the hydroxyl and proton acceptors and significantly\npromote the transformation of intermediate species and charge transfer\nprocesses in both the OER and HER. The Ni­(OH)₂/Ni₃S₂/NF electrode shows overpotentials as low as 252, 279,\nand 319 mV to reach 30, 50, and 100 mA cm^–2, respectively,\nfor OER and 48, 79, and 185 mV to achieve 10, 20, and 100 mA cm^–2, respectively, for HER in 1.0 M KOH solution. An\nalkaline electrolyzer assembled by bifunctional Ni­(OH)₂/Ni₃S₂/NF electrodes displays cell voltages\nof 1.80 V to deliver 100 mA cm^–2 and is stable for\nover 100 h. This study demonstrates promising potential of the Ni­(OH)₂/Ni₃S₂/NF bifunctional electrode for\nadvancing water-splitting technologies.