Electrospun CoFe₂O₄ Nanowires Tailored for Magnetoelectrochemistry.

Abstract

In view of a future green hydrogen economy, the development of efficient, platinum-group-metal-free catalysts for the oxygen evolution reaction (OER) remains an important goal. Magnetic enhancement of oxygen-evolving catalysis is an interesting strategy to boost catalyst activity, as it can promote the formation of triplet oxygen through spin polarization. Magnetoelectrochemistry can rely on the use of an external magnetic field or the internal magnetic order of the catalyst. Therefore, synthesis strategies that allow for tailoring the magnetic properties of magnetic catalyst materials are of high interest. Here, we report on the synthesis of CoFe₂O₄ (CFO) nanowires through an electrospinning template strategy followed by calcination. The calcination temperature was found to have a profound impact on both the morphology and the magnetic properties of the materials, with a temperature of 1173 K yielding intergrown nanoparticles that formed a nanowire-like structure with excellent magnetic properties: a high saturation magnetization of 88.9 emu/g and a coercivity of 17 100 Oe at 2 K. Electron microscopy was employed to identify the temperature-dependent evolution of the microstructure of the synthesized CoFe₂O₄ anisotropic structures. Thereafter, the sample was studied as a catalyst for electrochemical OER in alkaline electrolyte, where its great performance was found to be further boosted by application of an external magnetic field of 500 mT, resulting in an enhancement by over 100% at a constant potential of 1.60 V_RHE, placing CFO-1173 K among the best-performing catalyst materials in terms of magnetocurrent.