Exploring the mechanisms of catalytic performance enhancement for HER and OER on nickel film by incorporating antimony atoms: DFT study and experimental validation

The proper design of earth-abundant bifunctional electrocatalysts for best-performing water electrolysis is exceptionally challenging. Herein, we investigated the mechanism of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on nickel film by incorporating antimony atoms to realize its overall water splitting performance. Density functional theory (DFT) predictions demonstrate that the incorporation of antimony with a two-dimensional structure to the nickel backbone could optimize free energies of intermediates during HER and OER processes, thereby modulating adsorption/desorption behaviors on the surface and ultimately accelerating the catalytic kinetics. The formation of an alloy structure causes the ΔGH* of NiSb film (-0.46 eV) is smaller compared to the pure Ni (-1.12 eV) and pure Sb (-1.43 eV), and also the rate-determining step (RDS) of OER becomes "OOH* → O2" instead of "O* → OOH*", so that the ∆GRDS is significantly reduced (from 2.1 eV for pure Ni to 1.7 eV for NiSb). Based on experimental validation, the NiSb exhibits low overpotentials of 298 mV and 473 mV at the current density of 100 mA.cm−2 toward the HER and OER in 0.5 M NaOH solution, benefiting from the collective plentiful active sites and the modulated electronic structure induced by alloying nickel and antimony. The obtained theoretical findings provide deep insights into the relationship between the catalytic properties of alloyed structures and intrinsic electronic configuration to design highly efficient catalysts for water splitting.