Interfacial Cooperation-Driven Shifts of Volcano Relationships in Ammonia Decomposition

Ammonia decomposition is governed by an intrinsic trade-off between NH 3 dehydrogenation and N–N coupling, giving rise to the well-known volcano relationship that has long positioned ruthenium (Ru) near the activity maximum. However, how metal–oxide interfacial cooperation influences this conventional volcano relationship remains poorly understood. Here we show that metal–oxide interfacial cooperation qualitatively alters the reaction pathway of ammonia decomposition. Using reaction-aware machine learning simulations, we find that on MgO(111)-supported metal nanoparticles, NH 3 dehydrogenation, one of the most kinetically demanding steps, occurs predominantly at the metal–oxide interface with substantially reduced activation barriers, while N–N coupling remains governed by the metal surface. This spatial separation of reaction bottlenecks relaxes the classical single-site trade-off and drives a shift of the activity volcano toward weaker nitrogen-binding metals, thereby rendering earth-abundant catalysts highly competitive. As a consequence, Ni supported on MgO(111) emerges near the shifted activity optimum, while Cu also shows strong predicted performance; both are predicted to surpass Ru. Our results reveal how interfacial cooperation reshapes catalytic energetics in the metal/MgO(111) systems studied here, offering mechanistic insight to guide the design of earth-abundant catalysts beyond the conventional single-site paradigm.