Overall water splitting into hydrogen and oxygen using electrocatalysts could potentially address the large-scale energy needs of future societies, since H₂ generated can be utilized in fuel cells to generate electricity. However, water splitting itself is a thermodynamically unfavorable process, which is further complicated by the high overpotential for H₂ and O₂ evolution on many electrocatalysts surfaces. Using a single bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalyst is challenging since the same material must be able to effectively catalyze both the HER and OER whilst achieving a low overall overpotential and as high a current density as possible.

Tierui Zhang, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China, and colleagues have reported Ni₃FeN nanoparticles (Ni₃FeN-NPs) with a particle size of 100 nm and a thickness of ~9 nm synthesized by thermal ammonolysis of ultrathin NiFe- layered double hydroxide (LDH) nanosheets. The Ni₃FeN-NPs show extraordinarily high activities for both HER and OER with low overpotentials and Tafel slopes, which exhibited better activity than most other noble-metal-free electrocatalysts and commercial Pt/C in overall water splitting. The excellent performance of Ni₃FeN-NPs derives from the intrinsic metallic character and unique electronic structure of this compound which improve the electrical conductivity and adsorption of H₂O, and also the nanosized particle effects which increase the availability of active sites for electrocatalysis.

This work provides a promising noble metal-free platform electrocatalytic splitting water to H₂ energy and prompts further investigations into bimetallic nitride systems for energy conversion.