Earth-Abundant Manganese Nitride Catalysts for Mild-Condition Ammonia Synthesis

Developing advanced catalytic materials for mild-condition ammonia (NH₃) synthesis is essential for improving the energy efficiency of the industrial Haber-Bosch process. Here, we report a ζ-phase manganese nitride (MnN_0.43) catalyst for low-temperature NH₃ synthesis. The as-synthesized MnN_0.43 catalyst is protected by a carbon shell, allowing for the storage and processing of the air-sensitive metal nitride under ambient conditions. After activation in situ, the MnN_0.43 catalyst exhibits high activity for NH₃ synthesis at 250–350 °C, surpassing the conventional noble metal based Ru/MgO catalyst. A combination of kinetic, chemisorption, isotope labeling and computational studies indicate that a nitrogen vacancy-mediated associative mechanism accounts for the catalytic enhancements. Our work highlights the great potential of earth-abundant transition metal nitrides for catalyzing mild-condition NH₃ synthesis.