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 VRHE, placing CFO–1173 K among the best-performing catalyst materials in terms of magnetocurrent.The authors thank Dr. András Kovacs for the initial electron microscopy study. This work was supported by the European Union’s Horizon 2020 research and innovation program through the SpinCat Project under grant agreement no. 964972 and through the KNOWSKITE-X Project under grant agreement no. 101091534. L.M.S. acknowledges financial support through the Ramón y Cajal grant RYC2020-030414-I funded by MICIU/AEI/10.13039/501100011033 and by “ESF Investing in your future”