Ammonia Synthesis on the RRuSi(001) (R = Ca,La) Surfaces: DFT Insights Revealing the Active La Termination of the LaRuSi Electride

Recently, transition metal electrides have attracted the attention of scientists as promising catalysts for ammonia synthesis. But very little is known about the atomic processes involved. In this work, extensive DFT calculations have been performed to explore the detailed mechanism of ammonia synthesis on LaRuSi, a typical electride catalyst. Unlike previous studies involving the LaRuSi(001) high energy Ru-terminated surface, we propose here an alternative reaction path at the most stable La termination. Our study addresses the contrasted catalytic properties of the isostructural LaRuSi electride and CaRuSi non-electride compounds. It points to the role of surface La atoms in the catalytic performances of LaRuSi and shows that active sites are not necessarily transition metal atoms. Our findings open up future explorations of transition metal free catalysts for ammonia synthesis, active under mild conditions.