Dynamic and electrified ammonia synthesis enabled by magnetic heating of barium-promoted ruthenium catalyst

Ammonia synthesis is a cornerstone of the chemical industry, but conventional methods rely on energy-intensive processes coupled to fossil fuels. Electrified, dynamically responsive ammonia synthesis that can rapidly adapt to fluctuating operating conditions, especially power input, is highly sought after to align with intermittent renewable energy sources such as solar or wind. Here, we demonstrate that a well-designed magnetic nanocatalyst – specifically, a Ba-promoted, Ru-decorated Co_0.67Ni_0.33-Al₂O₃ nanocomposite – provides localized heating at active sites. This enables rapid start-up (less than 10 min to achieve maximal ammonia productivity), a high synthesis rate exceeding 1500 mmol NH₃ g_Ru⁻¹ h⁻¹ at 350 °C and 5.5 MPa, and stable operation for at least 120 h. Kinetic analysis combined with calorimetric measurements reveals that magnetic heating induces pronounced local overheating, with effective temperatures at the catalytically active sites exceeding the thermocouple-measured bed temperature by more than 100 °C. This significant local overheating provides a mechanistic explanation for the observed high reaction rates and rapid dynamic response. Density functional theory and microkinetic modelling show that Ba promotion lowers the nitrogen dissociation barrier at Ru–BaO interfaces, enhancing activity. Our results highlight the synergistic role of magnetic heating and the Ru–BaO interface in accelerating ammonia synthesis under mild conditions and establish a foundation for dynamic, sustainable catalysis powered by renewable electricity.