Magnetic-Field-Induced Large OER Enhancement in Co-Based Ferrimagnetic Thin Films

Abstract Electrochemical water splitting offers a promising route to sustainable hydrogen production, yet the oxygen evolution reaction (OER) remains kinetically sluggish and subject to spin-selection constraints associated with triplet O2. Here, CoTb ferrimagnetic thin films with strong perpendicular magnetic anisotropy (PMA) are used to investigate the relationship between magnetic ordering and OER kinetics. Under a 300 mT magnetic field, the onset potential decreases by ∼96 mV and the Tafel slope by ∼15.1 mV·dec–1, accompanied by reduced charge-transfer resistance. The enhanced OER activity is strongly correlated with magnetic-state regulation and largely retained after field removal. Tb-mediated 3d–4f exchange and strong PMA contribute to regulating and retaining the Co magnetic state, which may influence interactions between Co active sites and oxygen intermediates. This nonvolatile magnetic state may eliminate the need for continuous field application, potentially reducing energy consumption. These findings provide a new perspective for magnetically regulated electrocatalysts.