<p>Rational design of active oxygen evolution
reaction (OER) catalysts is critical for the overall efficiency of water
electrolysis. OER reactants and products’ differing spin states is one of causes
to slow OER kinetics. Thus, spin conservation plays a crucial role in enhancing
OER performance. In this work, we design ferromagnetic (FM)–antiferromagnetic
(AFM) Fe<sub>3</sub>O<sub>4</sub>@Ni(OH)<sub>2</sub> core–shell catalysts. The
interfacial FM–AFM coupling of these catalysts facilitates selective removal of
electrons with spin direction opposing the magnetic moment of FM core,
improving OER kinetics. The shell thickness is found critical in retaining the
coupling effect for OER enhancement. The magnetic domain structure of the FM core also plays
a critical role. With a multiple domain core, the applied magnetic field aligns
the magnetic domains, optimising the electron transport process. A significant
enhancement of OER activity is observed for the multiple domain core catalysts.
With a single domain FM core with ordered magnetic dipoles, the spin-selective
electron transport with minimal scattering is facilitated even without an
applied magnetic field. We therefore draw a magnetism/OER activity model that
depends on two main parameters: interfacial spin coupling and domain structure.
Our findings provide new design principles for active OER catalysts.</p>
