Uncovering the Role of Intrinsic Magnetic Order in OxygenEvolution Reaction Activity with Operando Spectroscopy

Understanding the role of intrinsic magnetic order on the oxygen evolution reaction (OER) requires careful consideration of the magnetic properties of both the catalytic surface and bulk under operating conditions. Because these often diverge from those of the pristine material, operando characterization that directly links magnetic behaviour to catalytic activity is essential. Here, we investigate the magnetic properties of La0.67Sr0.33MnO3 thin‐film OER catalysts using a combination of temperature‐dependent operando ferromagnetic resonance spectroscopy (FMR), ambient‐pressure X‐ray magnetic circular dichroism (XMCD), and operando X‐ray absorption spectroscopy (XAS). A direct correlation between changes in long‐range magnetic order and OER activity, with minimal changes in the catalyst’s electronic state was observed. Non‐interacting ferromagnetic regions were found to enhance activity at temperatures just above the Curie temperature. The enhancement is further amplified when the thin film undergoes the bulk paramagnetic‐to‐ferromagnetic transition below the Curie temperature. Our results indicate that interatomic spin‐exchange interactions, occurring within ferromagnetic regions and across the ferromagnetic bulk, and between these atoms and adsorbates, dominate the observed OER enhancements, potentially augmented by short‐range spin‐polarized conduction effects. These findings highlight that local ferromagnetic order, governed by exchange interactions over a few unit cells, plays a crucial role in modulating surface reaction dynamics, offering mechanistic insight into spin‐dependent catalysis.