Weakly Anisotropic Surface States Boost Ru Dispersion and Ammonia Synthesis

Abstract Electrides have been recognized as highly effective catalyst systems for ammonia synthesis at mild conditions. Most previous studies have focused on exploring new electride‐based catalysts, leaving the surface utilization largely unexplored. Here, the ternary BaAlSi electride, with weakly anisotropic surface states, is reported to exhibit excellent Ru dispersity and superior catalytic performance. Investigations reveal a weakly preferred crystal orientation in BaAlSi and little different adsorption energies for Ru over various surfaces, facilitating uniform growth of Ru nanoparticles. Each surface of BaAlSi exhibits a low work function ( Φ WF ), enhancing electron transfer to Ru and activating N 2 . Additionally, surface Ba migration effectively inhibits Ru aggregation, allowing particle sizes to be controlled at 2−3 nm, significantly improving Ru utilization. Consequently, even with a small surface area (∼1 m 2 g −1 ), the catalytic activity of Ru/BaAlSi surpasses that of other Ru/electride catalysts, achieving a high NH 3 production rate of 550 mmol g −1 Ru h −1 and a turnover frequency of 0.35 s −1 at 400 °C and 0.1 MPa, showcasing its application potentials. These findings not only provide valuable insights into designing novel electride‐based catalysts for efficient ammonia synthesis but also potentially inspire further research on surface engineering for creating isotropic surface states for heterogeneous catalysis.