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 this key industrial process. Here, we report a ζ-phase manganese-nitride (MnN0.43) catalyst for low-temperature NH3 synthesis. The as-synthesized MnN0.43 catalyst is protected by a carbon shell, allowing for storage and processing of the air-sensitive metal nitride under ambient conditions. After activation in situ, the MnN0.43 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 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.