Designing Nanoarchitecture of NiCu Dealloyed Nanoparticles on Hierarchical Co Nanosheets for Alkaline Overall Water Splitting at Low Cell Voltage

A nanoarchitecture is designed by percolation dealloying of NiCu alloy on Co nanosheets and used as efficient electrocatalyst for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting in an alkaline medium. The optimized NiCu/Co nanocomposite catalyst shows attractive activities of HER and OER with low overpotentials and Tafel slopes and with high mass activities, turnover frequencies, and exchange current densities, respectively. When applied to overall water splitting in a two electrode electrolyzer, the optimized can reach 10 mA cm^–2 at cell voltages of only 1.46 and 1.51 V in 1.0 M and 30 wt % KOH, respectively, much lower than those of commercial IrO₂||Pt/C. It can reach current density of >1000 mA cm^–1 at low voltage. Proposed mechanisms are proven and corroborated with experimental and computational studies. Selective leaching of NiCu alloy produced nanoporous Cu-rich alloy, which actively participated as an active site for HER with lowest ΔG(H*) of 0.02 eV. The active sites on high energy (100) surface exposed Co NS actively participated in four electrons uphill OER as the adsorption sites for active species (*O, *OH, and *OOH) because Co d-bands dominate the region close to the Fermi level. Availability of separate sites and their synergy make the nanocomposite work at the lowest cell voltage with high mass activity.