Magnetic NiFe₂O₄ Nanoparticles Prepared via Non‐Aqueous Microwave‐Assisted Synthesis for Application in Electrocatalytic Water Oxidation

Abstract

Phase-pure spinel-type magnetic nickel ferrite (NiFe₂ O₄ ) nanocrystals in the size range of 4 to 11 nm were successfully synthesized by a fast and energy-saving microwave-assisted approach. Size and accessible surface areas can be tuned precisely by the reaction parameters. Our results highlight the correlation between size, degree of inversion, and magnetic characteristics of NiFe₂ O₄ nanoparticles, which enables fine-tuning of these parameters for a particular application without changing the elemental composition. Moreover, the application potential of the synthesized powders for the electrocatalytic oxygen evolution reaction in alkaline media was demonstrated, showing that a low degree of inversion is beneficial for the overall performance. The most active sample reaches an overpotential of 380 mV for water oxidation at 10 mA cm^-2 and 38.8 mA cm^-2 at 1.7 V vs. RHE, combined with a low Tafel slope of 63 mV dec^-1 .