Realizing the key role of magnetic domain walls in magnetic field-enhanced oxygen evolution reaction

Understanding the relationship between magnetic structures (magnetic domains and domain walls) and enhanced activity is crucial for elucidating the mechanism behind magnetic field-assisted oxygen evolution reaction (OER). In this work, two-dimensional CoSe2 nanosheets with room-temperature ferromagnetic properties and structural stability were synthesized using chemical vapor deposition. Electrochemical measurements suggest that OER performance of CoSe2 nanosheets is improved under a 200 mT magnetic field, with the overpotential at 10 mA cm−2 reduced by 81 mV. Moreover, magnetic force microscopy observations on CoSe2 nanosheets reveal that spin disorder in the magnetic domain wall region transforms to spin order under the 200 mT magnetic field, resulting in improved OER performance. Although the magnetic field has a negligible effect on the OER performance of single-domain CoSe2 nanosheets, these findings reveal the decisive role of magnetic domain walls in enhancing OER performance under an applied magnetic field, pointing to the potential for industrial applications of magnetic field-assisted catalysis.