调控磁导率以优化高熵合金的自旋电子排列实现高效析氧反应

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

磁场触发的催化剂轨道电子自旋排列已成为促进析氧反应的一种有趣而可行的策略.然而,具有强d-d库仑相互作用的高熵合金(HEAs)催化剂中的磁场增强机制尚未得到充分挖掘.在此,我们设计了具有优异软磁性的高熵合金金属片,在微小磁场下表现出显著的磁场增强催化作用,其磁导率可作为评估磁场增强的描述因子.具体地,仅施加50 mT的磁场,(FeCoNi)_(82.5)Cr_(17.5)HEAs的过电位下降就超过了36mV@10 mA cm^(-2).此外,过电位的降低与HEA的磁导率呈线性关系.原位拉曼光谱与理论计算结果表明,施加磁场可显著提高自旋密度,改善催化剂的3d电子与*O自由基的2p轨道之间的自旋相互作用,从而有效降低速率决定步骤(*O→*OOH)的能量障碍,进而促进O-O的形成.

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)_(82.5)Cr_(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.