Optimizing spin arrangement by permeability modulation of high-entropy alloys to promote O-O formation for efficient water oxidation

Magnetic field-triggered spin arrangements have emerged as an intriguing and viable strategy for enhancing the oxygen evolution reaction. However, the magnetic field-enhanced mechanism in high-entropy alloy (HEA) catalysts with strong d-d Coulomb interactions remains incompletely understood. In this study, metal-sheet HEAs with excellent soft-magnetic properties that exhibit remarkable field-enhanced catalysis under a minute magnetic field were designed. The permeability of these HEAs serves as a descriptor for assessing the enhancement. Specifically, the drop in the overpotential of (FeCoNi)_82.5Cr_17.5 HEAs exceeds 36 mV@10 mA cm⁻² when applying a field of only 50 mT. Furthermore, reduction in overpotential demonstrates a direct linear correlation with the magnetic permeability of the HEAs. Theoretical calculations coupled with in-situ Raman spectroscopy elucidate that applying a magnetic field substantially significantly increases spin density and improves the spin interaction between the 3d electrons of the catalyst and the 2p orbital of the *O intermediate. This effectively lowers the energy barrier of the rate-determining step (*O→*OOH), thereby facilitating O-O formation.