Novel one-step synthesis of core@shell iron–nickel alloy nanoparticles coated by carbon layers for efficient oxygen evolution reaction electrocatalysis.

As a crucial reaction of electrochemical water splitting, oxygen evolution reaction receives intensive and significant attention in recent years. Here, we develop a type of electrocatalyst with core@shell structure in the form of binary FeNi alloy nanoparticles coated by highly defective nitrogen-doped carbon shell with mesoporous architecture. The composite annealed at 800 °C with Fe/Ni ratio of 1:2 presents extremely high catalytic activity and durability for oxygen evolution in 1.0 M KOH electrolyte, which delivers a low overpotential of 273 mV to achieve a current density of 10 mA cm−2 and a small Tafel slope of 37.82 mV dec−1. We find that appropriate Fe-doping to regulate the surface electronic structure around the active sites is responsible for boosting the electrocatalytic performance. Remarkably, hydroxyl groups introduced along with the Fe doping, acting as an active O radical to facilitate the adsorption of intermediates, are identified as another decisive factor to promote the intrinsic activity for the oxygen evolution reaction. Moreover, such an N-doped carbon shell endows the composite with enriched defects, high conductivity and satisfactory stability, favoring fast electron transfer kinetics. The substantially high catalytic performance of the fabricated binary metallic electrocatalyst makes it potential application in energy storage and conversion devices. Image 1 • 2-methylimidazole is usded for the formation of Fe and Ni complexes. • FeNi alloy nanoparticles coated by nitrogen-doped carbon shell are prepared. • The FeNi composite exhibits high catalytic performance for OER. • Low overpotential of 273 mV is needed to achieve current density of 10 mA cm−2 [ABSTRACT FROM AUTHOR]