Enhanced ammonia synthesis activity of Ru/Ba5Ta4O15 catalyst by reduction of Ba5Ta4O15 with CaH2.

Recently, lattice defects (hydrogen vacancies, oxygen vacancies and nitrogen vacancies) have attracted significant attention due to their promoted activity of ammonia synthesis. Here, composites of CaBTO were prepared via treatment of Ba 5 Ta 4 O 15 –CaH 2 mixture in a flow of H 2 /N 2 at 600 °C for 16 h. It was found that the reduction of Ba 5 Ta 4 O 15 by CaH 2 significantly promoted the ammonia synthesis activity of Ru/Ba 5 Ta 4 O 15. The oxygen vacancies (O v) with trapped electrons were formed in CaBTO. Various characterizations and kinetic experiments indicated that O v donated electrons to Ru particles to promote the activation and dissociation of N 2 , and accepted the hydrogen atoms from Ru surface to suppress hydrogen poisoning. The lattice N3− and H− in CaBTO could also accept hydrogen or nitrogen atoms to form NH 3 , which provided more reaction pathways for ammonia synthesis and further improved the rate of ammonia synthesis. [Display omitted] • N3−, H− and O V were introduced in Ba 5 Ta 4 O 15 by reduction of Ba 5 Ta 4 O 15 with CaH 2. • Hydrogen poisoning of Ru species was alleviated through hydrogen spillover. • NH x (x = 1–3) species could form on the Ru surface and CaBTO600. [ABSTRACT FROM AUTHOR]