Barium Oxynitride Electride as Highly Enhanced Promotor for Ruthenium Catalyst in Ammonia Synthesis: Comparative Study with Barium Oxide

• Published in: Advanced energy materials 2023-12, Vol.13 (45), p.n/a
• Main Authors: Li, Jiang, Jiang, Yihao, Zhang, Zhujun, Tsuji, Masatake, Miyazaki, Masayoshi, Kitano, Masaaki, Hosono, Hideo
• Format: Article
• Language: English
• Subjects: Ammonia; ammonia synthesis; barium oxide; Barium oxides; Catalysts; Chemical synthesis; Comparative studies; electride; Electrons; oxynitride; Oxynitrides; Ruthenium; ruthenium catalysts
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202302424

Barium oxide is a conventional promoter for various transition‐metal (TM) catalysts in ammonia synthesis. Ba‐promoted Ru catalysts are widely used for ammonia synthesis under mild reaction conditions. However, the promotion mechanism, including the active factor, remains unclear. In this study, the excellent promotion effect of barium oxynitride is reported, which creates anionic electrons in the lattice, forming an electride (BaOxNy:e−z) with the same rocksalt structure as BaO. The BaOxNy:e−z enhances the ammonia synthesis activity of the supported Ru catalyst by 40–100 fold compared with the BaO promotor. This study reveals that a low‐work‐function electron formed in the BaO lattice plays a pivotal role in the electronic promotion effect in catalytic ammonia synthesis, suggesting that BaOxNy:e−z formed near the surface during the ammonia synthesis reaction is an active species for the promotion effect of conventional BaO. A barium oxynitride electride (BaOxNy:e−z) greatly enhances the activity of a Ru catalyst for ammonia synthesis by 40–100 fold compared with BaO and dramatically reduces the reaction barrier, demonstrating the importance of incorporated low‐work‐function electrons in the BaO lattice for the electronic promotion effect in ammonia synthesis.