Intermetallic Electride Catalyst as a Platform for Ammonia Synthesis

Electrides loaded with transition-metal (TM) nanoparticles have recently attracted attention as emerging materials for catalytic NH3 synthesis. However, they suffer from disadvantages associated with the growth and aggregation of nanoparticles. TM-containing intermetallic electrides appear to be promising catalysts with the advantages of both electrides and transition metals in a single phase. LaRuSi is reported here to be an intermetallic electride with superior activity for NH3 synthesis, and direct evidence is provided supporting its electride-character-induced catalytic performance. The discussion is made mainly based on the contrasting synthesis rates over the isostructural compounds LaRuSi, CaRuSi, and LaRu2Si2, and the N-2 isotope-exchange reactions over these compounds. Lattice hydride ions, which can reversibly exchange with anionic electrons, are shown to be indispensable in the promotion of NHx formation. The mechanism derived from the present findings provides new guidelines for NH3 synthesis.