Integrating Dissociative and Associative Routes for Efficient Ammonia Synthesis over a TiCN-Promoted Ru-Based Catalyst

Dinitrogen activation in ammonia (NH3) synthesis usually obeys either the dissociative or associative route. We report here a combination of dissociative and associative routes over a titanium carbonitride (TiCN)-promoted Ru-based catalyst to achieve an outstanding NH3 synthesis rate. The developed Ru/3TiCN/ZrH2 catalyst shows a superior NH3 synthesis rate of 25.6 mmol g(cat)(-1) h(-1) at 400 degrees C and 1 MPa. Our studies reveal that TiCN transfers electrons to the Ru centers and reduces the aggregation of Ru metal particles to generate more B5 sites, thus accelerating the dissociation of N-2 to form NH3 via a dissociative route. Meanwhile, the facile formation of nitrogen vacancies on TiCN assisted by Ru enables the associative mechanism initiated with N-2 hydrogenation to form *NNH. The synergistic effect of Ru and TiCN on N-2 activation via integrating the dissociative and associative mechanisms accounts for the superior NH3 synthesis rate of our catalyst under mild conditions.