Plasma-assisted in situ engineering of bimetallic phosphate coated Ni(OH)2–CuO nanosheets for robust electrocatalytic hydrogen evolution

Abstract

Hydrogen production by water electrolysis is a promising green and sustainable energy source, and engineering low-cost and high-efficiency electrocatalysts is crucial to ensure reliable and abundant global energy supply. Herein, a new and effective approach for electrocatalyst production for robust hydrogen evolution reaction (HER) is reported. The Ni–Cu hydroxide and oxide nanosheets are directly synthesized on the plasma-treated nickel foam (PNF) substrate, and then the ultrathin layer of transition metal phosphate is electrodeposited. The CuO and Ni(OH)2 heterostructures effectively enrich the catalytically active sites, reduce the HER free energy while greatly increasing the conductivity, thus causing the high HER activity. Meanwhile, the multilayer nickel-cobalt phosphate not only accelerates the HER reaction kinetics, but also acts as a protective layer, which greatly improves the electrode stability. The overpotential of the synthesized NiCo–P@CuO–Ni(OH)2/PNF catalyst is 59 mV (Tafel slope is 51.4 mV dec−1) for HER driven with a current density of 10 mA cm−2 (j10) in 1.0 M KOH electrolyte. Importantly, the nanostructure and sustainable activity of NiCo–P@CuO–Ni(OH)2 are retained after a 100 h HER process under the simulated industrial conditions. The Density Functional Theory and in situ Raman results reveal that the nickel sites exposed at the CuO–Ni(OH)2 heterointerface act as the HER catalytically active centers.