Ternary intermetallic LaCoSi as a catalyst for N2 activation

Abstract

Activating high-energy multiple bonds using earth-abundant metals is one of the most significant challenges in catalysis. Here, we show that LaCoSi—a ternary intermetallic compound—is an efficient and stable catalyst for N2 activation to produce NH3. The ammonia synthesis is significantly promoted by shifting the reaction bottleneck from the sluggish N2 dissociation to NH x formation, which few catalysts have achieved. Theoretical calculations reveal that the negatively charged cobalt mediates electron transfer from lanthanum to the adsorbed N2, which further reduces the activation barrier of N2 dissociation. Most importantly, the specific LaCoSi geometric configuration stabilizes the N2 adsorption with a strong exothermic effect, which dramatically decreases the apparent energy barrier of N2 activation. Consequently, LaCoSi shows a superior activity (1,250 μmol g−1 h−1), with a 60-fold increase over the activity of supported cobalt catalysts under mild reaction conditions (400 °C, 0.1 MPa). Ammonia synthesis is an energy-intensive process due to the high activation barrier for N2 dissociation. Here, Hosono and co-workers show that the intermetallic compound LaCoSi can lower the energy requirement for N2 activation and shift the rate-determining step of the process to NH x formation under mild conditions.