A facile self-magnetic-attracted approach was developed for highly active and stable NixFe(1-x)@NixFe(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 NixFe(1-x)@NixFe(1-x)O core-shell nanocrystals with superparamagnetism. Then, these NixFe(1-x)@NixFe(1-x)O nanoparticles (NPs) could be easily supported on nickel foam without any binders or additives. Optimized by the composition effect, the Ni0.7Fe0.3@Ni0.7Fe0.3O/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 NixFe(1-x)@NixFe(1-x)O NPs also serve an ideal building block for fundamental research of nickel-iron based catalyst.
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Globin-like mesoporous CeO2 has been constructed by using a CO-assisted synthetic approach based on hydroxide carbonate precursors, in which CO plays a key role in the formation of the globin-like mesoporous precursors as the carbon source because of its preferential adsorption on Ce3+ under the hydrothermal conditions. The formation mechanism and the thermal transformation process from globin-like mesoporous CeCO3OH to CeO2 have been investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, BET surface area measurements, thermal analysis, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy. Rod-like building blocks interconnected by nanoparticles circle around to form each globin-like CeO2 spheres, leading to the formation of a mesoporous structure. The globin-like mesoporous CeO2 shows much better performance in CO catalytic oxidation than ordinary CeO2 nanoparticles obtained by directly calcining cerium nitrate. Moreover, the globin-like mesoporous CeO2 can act as an ideal matrix for supported catalysts. Metallic Au particles can be well dispersed in the globin-like CeO2 matrix to form Au/CeO2 supported catalysts, which exhibit excellent activity for CO oxidation at room temperature.