Intermetallic Electride Catalyst as a Platform for Ammonia Synthesis

Abstract

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 LaRu₂ Si₂ , and the N₂ 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 NH_x formation. The mechanism derived from the present findings provides new guidelines for NH₃ synthesis.