Alternating Magnetic Field Promotes Ammonia Cracking by Disrupting the Sabatier Limitation of Ruthenium Catalytic Species

When catalyzing a reaction comprising elementary reaction steps that demand both strong and weak adsorption of sequential intermediates to complete a full cycle, catalytic metals often exhibit reactivity compromises, known as Sabatier constraints. Herein, computational and experimental findings suggest that dynamic modulation of the catalyst spin state can provide a new handle to overcome such limitations via low- and high-spin catalysis for ammonia decomposition, which is a reaction that exemplifies Sabatier constraints due to the difficulty in achieving strong NH 3 binding as well as weak *H and *N binding for efficient H 2 and N 2 formations, respectively. We demonstrate that the self-heating ferrimagnetic Ru/Fe 3 O 4 catalyst operating under an alternating magnetic field (AMF) exhibits at least a 5-fold enhancement in activity relative to standard thermal operation below 400 °C. The key benefit comes from the time-varying magnetic flux within the catalyst under AMF, enabling rapid electronic responses at the Ru sites that mitigate Ru nitridation by transiently inducing a high-spin configuration of the metal. These findings highlight AMF-driven catalysis as a general reaction strategy for dynamically regulating catalyst electronic states and, in turn, surface intermediates, thereby overcoming the often-encountered Sabatier constraints in various catalytic reactions.