Optical Transduction of Magnetically Controlled Spin‐Selective Oxygen Evolution at a Ferrimagnetic Heterointerface

ABSTRACT Spin‐dependent pathways play a critical role in the oxygen evolution reaction (OER), yet direct and dynamic probing of spin‐selective catalysis remains challenging. Here we report an optical transduction strategy that provides a real‐time, chemically responsive readout of magnetically controlled spin‐selective OER. A ferrimagnetic Fe 3 O 4 /CoFe 2 O 4 heterointerface is engineered to establish a spin‐selective charge transport pathway, where interfacial magnetic coupling enables efficient field‐induced domain alignment under an external magnetic field. Electrochemical measurements and spin‐resolved calculations suggest that interfacial spin polarization favors triplet‐related oxygen evolution. Coupling this process to luminol electrochemiluminescence (ECL) translates changes in OER‐derived oxygen‐precursor availability into a reversible and peak‐selective optical signal through oxygen‐derived reactive species. The pronounced reverse‐scan enhancement provides a chemically amplified optical output of the magnetically regulated catalytic state, enabling dynamic optical transduction of spin‐dependent electrocatalysis. This work establishes a general framework for coupling spin‐dependent electrocatalysis with a chemically responsive optical readout, providing new opportunities for probing and controlling interfacial reactions through spin polarization.