Mechanistic Insights into Magnetic Field-Induced OER Enhancement via Magnetization Cycle Analysis

Disentangling non-spin-dependent and spin-dependent contributions to magnetic field-induced oxygen evolution reaction (OER) enhancement remains challenging due to the difficulty in quantifying magnetic flux density near catalytic surfaces, which depends on both the applied field and the intrinsic magnetic properties of the catalyst. Herein, 2:17-type samarium-cobalt magnets (Sm2Co17) with different initial magnetization states were evaluated in an electromagnet-integrated flow cell, employing magnetization cycle analysis to elucidate how intrinsic magnetic properties and magnetization state influence OER enhancement. Analysis of the potential shift (ΔE) throughout a complete magnetization cycle reveals butterfly shaped hysteresis, with characteristic loop features providing mechanistic insights. Bulk magnetic properties influence the loop contour via spin-pinning effects, whereas surface composition and magnetization state govern the linear ΔE shifts. The slope (κ) of the linear ΔE shifts serves as a descriptor of the catalytic surface response to magnetic field, enabling ΔE determination at a given field strength. Together, κ and the butterfly-shaped loop characteristics provide a potential analytical framework for quantifying magnetic field-induced OER enhancement and may offer insights into the magnetic properties of catalytic surfaces that emerge exclusively under OER conditions.