Co-Doped NiN Nanosheets with Electron Redistribution as Bifunctional Electrocatalysts for Efficient Water Splitting.

Preparation of high-activity and earth-abundant bifunctional catalysts for efficient electrochemical water splitting are crucial and challenging. Herein, Co-doped NiN nanosheets loaded on nickel foam (Co-NiN) were synthesized. The as-prepared Co-NiN exhibits excellent catalytic activity toward both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline media. Density functional theory (DFT) calculation reveals that Co-NiN with redistribution of electrons not only can facilitate the HER kinetics but also can regulate intermediates adsorption energies for OER. Specifically, the Co-NiN exhibits high efficiency and stable catalytic activity, with an overpotential of only 30 and 270 mV at a current density of 10 mA cm for the HER and OER in 1 M KOH, respectively. This work provides strong evidence to the merit of Co doping to improve the innate electrochemical performance in bifunctional catalysts, which might have a common impact in many similar metal-metal nitride electrocatalysts.