3D Nitrogen‐Anion‐Decorated Nickel Sulfides for Highly Efficient Overall Water Splitting

Abstract

Developing non-noble-metal electrocatalysts with high activity and low cost for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is of paramount importance for improving the generation of H₂ fuel by electrocatalytic water-splitting. This study puts forward a new N-anion-decorated Ni₃S₂ material synthesized by a simple one-step calcination route, acting as a superior bifunctional electrocatalyst for the OER/HER for the first time. The introduction of N anions significantly modifies the morphology and electronic structure of Ni₃S₂, bringing high surface active sites exposure, enhanced electrical conductivity, optimal HER Gibbs free-energy (ΔG_H*), and water adsorption energy change (ΔG_H2O*). Remarkably, the obtained N-Ni₃S₂/NF 3D electrode exhibits extremely low overpotentials of 330 and 110 mV to reach a current density of 100 and 10 mA cm⁻² for the OER and HER in 1.0 m KOH, respectively. Moreover, an overall water-splitting device comprising this electrode delivers a current density of 10 mA cm⁻² at a very low cell voltage of 1.48 V. Our finding introduces a new way to design advanced bifunctional catalysts for water splitting.