Atomic-scale Al doping to suppress Ru volatilization and break the volcanic activity barrier in ammonia synthesis catalysts

초록

Noble metals are essential for transformative catalytic processes—from conventional to renewable fuel production—yet their scarcity imposes critical constraints on large-scale implementation. Ruthenium (Ru) is among the most effective catalytic components for ammonia (NH3) synthesis under mild conditions; however, achieving high atomic efficiency remains challenging. Although Ru-Ba/MgO catalysts are highly active, they exhibit volcanic activity trends with respect to the Ba/Ru ratio, indicating inherent structural limitations. Here, we identify that the sublimation of Ru3(CO)12 results in significant Ru loss during catalyst synthesis. To address this challenge, we introduce trace aluminum (Al) doping into the Ru-Ba/MgO system to create Ru-Ba/MgAlOx catalysts. Comprehensive experimental and computational analyses reveal that trace amounts of atomically dispersed Al species on the BaO and MgO domains change the Ru precursor decomposition/activation pathway, thereby suppressing Ru volatilization. The optimized Ru-Ba/MgAlOx catalyst shows approximately 1.6-fold higher NH3 synthesis activity than the optimized Al-free counterpart, thereby overcoming the conventional volcanic activity barrier. This enhancement is attributed to the ideal Ru dispersion and the increased density of active Ru–BaO interfaces, facilitated by Al-induced Ru stabilization. This work proposes a rational strategy to maximize the efficiency of noble metals by utilizing earth-abundant elements. © 2026 Elsevier B.V.

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