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 dealloyingof NiCualloy on Co nanosheets and used as efficient electrocatalyst for hydrogenevolution reaction (HER), oxygen evolution reaction (OER), and overallwater splitting in an alkaline medium. The optimized NiCu/Co nanocompositecatalyst shows attractive activities of HER and OER with low overpotentialsand Tafel slopes and with high mass activities, turnover frequencies,and exchange current densities, respectively. When applied to overallwater splitting in a two electrode electrolyzer, the optimized canreach 10 mA cm(-2) at cell voltages of only 1.46 and1.51 V in 1.0 M and 30 wt % KOH, respectively, much lower than thoseof commercial IrO2||Pt/C. It can reach current densityof >1000 mA cm(-1) at low voltage. Proposed mechanismsare 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 & UDelta;G(H*) of 0.02 eV. The activesites on high energy (100) surface exposed Co NS actively participatedin four electrons uphill OER as the adsorption sites for active species(*O, *OH, and *OOH) because Co d-bands dominate theregion close to the Fermi level. Availability of separate sites andtheir synergy make the nanocomposite work at the lowest cell voltagewith high mass activity.