Synergistic Coupling of Ni Nanoparticles with Ni 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 Ni 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 Ni C nanosheets on carbon cloth (CC), and simultaneously couple with Ni nanoparticles, resulting in the formation of an integrated heterostructure catalyst (Ni-Ni C/CC). Benefiting from the superior intrinsic activity as well as the abundant active sites, the Ni-Ni C/CC electrode demonstrates excellent bifunctional electrocatalytic activities toward the OER and hydrogen evolution reaction (HER), which are superior to all the documented Ni C-based electrocatalysts in alkaline electrolytes. Specifically, the Ni-Ni C/CC catalyst exhibits the low overpotentials of only 299 mV at the current density of 20 mA cm for the OER and 98 mV at 10 mA cm for the HER in 1 m KOH. Furthermore, the bifunctional Ni-Ni 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.