Synergistic Coupling of Ni Nanoparticles with Ni₃ C Nanosheets for Highly Efficient Overall Water Splitting

Exploring earth-abundant bifunctional electrocatalysts with high efficiency for water electrolysis is extremely demanding and challenging. Herein, density functional theory (DFT) predictions reveal that coupling Ni with Ni₃ C can not only facilitate the oxygen evolution reaction (OER) kinetics, but also optimize the hydrogen adsorption and water adsorption energies. Experimentally, a facile strategy is designed to in situ fabricate Ni₃ C nanosheets on carbon cloth (CC), and simultaneously couple with Ni nanoparticles, resulting in the formation of an integrated heterostructure catalyst (Ni-Ni₃ C/CC). Benefiting from the superior intrinsic activity as well as the abundant active sites, the Ni-Ni₃ C/CC electrode demonstrates excellent bifunctional electrocatalytic activities toward the OER and hydrogen evolution reaction (HER), which are superior to all the documented Ni₃ C-based electrocatalysts in alkaline electrolytes. Specifically, the Ni-Ni₃ C/CC catalyst exhibits the low overpotentials of only 299 mV at the current density of 20 mA cm^-2 for the OER and 98 mV at 10 mA cm^-2 for the HER in 1 m KOH. Furthermore, the bifunctional Ni-Ni₃ C/CC catalyst can propel water electrolysis with excellent activity and nearly 100% faradic efficiency. This work highlights an easy approach for designing and constructing advanced nickel carbide-based catalysts with high activity based on the theoretical predictions.