Self-magnetic-attracted Ni_xFe_(1-x)@Ni_xFe_(1-x)O nanoparticles on nickel foam as highly active and stable electrocatalysts towards alkaline oxygen evolution reaction

A facile self-magnetic-attracted approach was developed for highly active and stable Ni_xFe_(1-x)@Ni_xFe_(1-x)O/NF electrocatalysts towards alkaline oxygen evolution reaction. Firstly, a low-cost and scalable synthesis method was developed to synthesis 4-5 nm hydrophilic Ni_xFe_(1-x)@Ni_xFe_(1-x)O core-shell nanocrystals with superparamagnetism. Then, these Ni_xFe_(1-x)@Ni_xFe_(1-x)O nanoparticles (NPs) could be easily supported on nickel foam without any binders or additives. Optimized by the composition effect, the Ni_0.7Fe_0.3@Ni_0.7Fe_0.3O/NF exhibits excellent activity for oxygen evolution reaction (OER), requires only 215 mV at 10 mA·cm^-2 and 260 mV at 100 mA·cm^-2, with a Tafel slope of 47.4 mV·dec^-1 in 1.0 M KOH. Moreover, the underlying mechanism was carefully studied by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectra (XANES) analysis and density functional theory (DFT) calculations. Due to the self-magnetic attraction, the catalyst shows outstanding stability throughout the electrocatalysis, surpassing than most self-supported catalysts. This work provides a new strategy for the construction of highly active and stable OER electrocatalysts, the nearly monodisperse magnetic Ni_xFe_(1-x)@Ni_xFe_(1-x)O NPs also serve an ideal building block for fundamental research of nickel-iron based catalyst.