Spin Migration-Driven Synergy in a Fe–Ba Dual-Atom Catalyst for Nitroaromatic Reduction

Selective reduction of nitroarenes to functional amines is a cornerstone transformation in organic synthesis, yet it remains challenging to achieve with earth-abundant metals under mild conditions. Here, we report a Fe–Ba dual-atom catalyst (FeBa-DAC) featuring pronounced Ba-induced electronic modulation of Fe. Incorporation of Ba into the N-doped carbon (NC) matrix is accompanied by a redistribution of spin density, with enhanced spin polarization on N atoms adjacent to Ba and a concomitant attenuation of carbon-centered spins in the presence of neighboring Fe sites. Combined spectroscopic and theoretical analyses suggest that this Ba-associated electronic and spin reorganization correlates with a lowered effective Fe valence state and an upshift of the Fe d-band center toward the Fermi level, thereby increasing electronic availability for σ* orbital coupling. Consequently, FeBa-DAC enables highly selective nitroarene reduction with hydrazine under ambient aqueous conditions, achieving substantially elevated intrinsic activity─nearly an order of magnitude higher than that of Fe single-atom catalysts and surpassing many state-of-the-art systems. Mechanistic studies reveal that hydrazine activation is the rate-determining step, and FeBa-DAC substantially lowers the corresponding energy barrier. These findings establish alkaline-earth metals as a powerful promoter for boosting Fe activity in dual-atom catalysts and provide molecular-level guidance for the rational design of advanced DAC systems.