Alkali Metal Template Effect Manipulates Dual-Site Cobalt–Molybdenum Catalyst Construction for Efficient Ammonia Synthesis

Alkali metals are recognized as effective additives to enhance catalytic activity in heterogeneous catalysis. Nevertheless, the traditional alkali metal promotion effect as electron donors cannot circumvent the linear scaling relationship between intricate reaction intermediates, and achieving highly efficient catalytic processes is still challenging. Herein, we propose an alkali metal template effect for the Co–Mo ensemble, which induces phase transition and intermetallic nanoparticle exsolution to construct a metal-nitride heterostructure. Detailed studies reveal that alkali metal atoms are embedded into the lattice of the oxide precursor rather than being electrostatically deposited over its surface, thus weakening the metal–oxygen interaction and facilitating nanoparticle exsolution from host materials. The prepared Co3Mo/Co2Mo3N catalyst delivers a superior activity of 12.3 mmol·gcat–1·h–1 for ammonia synthesis at 400 °C and 0.9 MPa, outperforming the well-recognized Co3Mo3N monophase nitride. We demonstrate that the enhanced activity is attributed to a dual-site mechanism for the independent activation of reactants on nitride and intermetallic surfaces rather than an electronic effect. These findings open perspectives for understanding the potential promotion effect of alkali metals and surpassing the Sabatier optimality.