Realizing Surface Spin Configurations of Two-Dimensional Fe7S8 for Oxygen Evolution Reaction

The surface spin configuration of catalysts is crucial for spin-dependent catalysis, as electrochemical reactions predominantly occur at the solid–liquid interface. This configuration influences reaction efficiency by altering the spin states of intermediates. Thus, identifying the surface spin configuration is essential for understanding the mechanisms affecting catalytic activity. This work designs multidomain and single-domain Fe7S8 nanosheets through thickness control. Under a 200 mT magnetic field, the multidomain sample transitions to a single-domain state, while the surface spin configuration of the single-domain sample remains unchanged, as observed via magnetic force microscopy. Electrochemical tests show that a saturated magnetic field of 200 mT reduces the overpotential of the multidomain sample from 306 to 240 mV at 10 mA cm–2, while the single-domain sample maintains an overpotential of 257 mV. These results demonstrate that spin disorder at magnetic domain walls limits spin selectivity during the OER, suggesting strategies for developing innovative spin-selective catalysts.