Spin-quenching cobalt center for efficient ammonia synthesis derived from oxide mixology

The spin polarization plays a critical role in heterogeneous catalysis by influencing the properties of active sites and thereby altering catalytic performance. However, precise construction of active sites with well-tuned spin states remains challenging. Here we demonstrate to manipulate the spin polarization of ferromagnetic cobalt (Co) centers in nitride catalysts by regulating the oxide mixology of precursors. The oxide mixology modulated the interaction between CoO_x and MoO₃ from local interfacial bonding to remote contacting. Strong and weak interactions induce the generations of Co₃Mo₃N and Co/γ-Mo₂N phases with low-spin and high-spin polarized Co centers, respectively, and Co centers with weakened spin polarization can facilitate the ammonia synthesis catalytic performance. Through the theoretical verification, we demonstrate that the spin-quenching configuration mitigates exchange splitting of Co centers, enabling efficient d-π* back-donation and enhancing N₂ activation. These findings open new perspectives for understanding the spin effect in heterogeneous catalysis and constructing well-defined spintronic catalysts.