In a recent study published in Angewandte Chemie International Edition, scientists developed an efficient ammonia synthesis catalyst consisting of atomically dispersed early transition metal Mn supported on the ternary hydride (LiBaH₃). The catalyst enables efficient ammonia synthesis through a hydride-assisted N₂ dissociation mechanism that circumvents traditional scaling relationships.

Ammonia synthesis is a cornerstone of modern agriculture and the chemical industry. It is regarded as a promising carbon-free energy carrier for a future hydrogen economy. However, the performance of conventional transition metal-based catalysts is constrained by the linear scaling relationship, which give rise to a volcano-type activity curve. Early transition metals such as Mn bind N too strongly, making the hydrogenation of activated *N species difficult. As a result, efficient ammonia synthesis catalysts based on early transition metals have rarely been reported.

The recent study, led by Prof. CHEN Ping from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. YUAN Shaojun from Sichuan University, overcame the bottleneck with a new catalyst: LiBaH₃–Mn₁.

In the catalyst, the activation of N₂ on Mn₁ sites prevents the direct dissociation of N₂ to form overly strong Mn–N bonds. Meanwhile, hydride ions (H⁻) from LiBaH₃ further activate the adsorbed *N₂ through a reductive protonation pathway, forming *N₂H intermediates. Subsequent N–N bond cleavage produces surface nitride (Mn–N) and imide (*NH) species on the LiBaH₃–Mn₁ interface.

The catalyst exhibited an ammonia synthesis rate two orders of magnitude higher than that of manganese nitride and performed 2.5 times better than the benchmark Cs-Ru/MgO catalyst at 400 °C, representing state-of-the-art performance among group 4–7 transition metal–based catalysts.

"Our study provides a new strategy for the rational design of highly active early transition metal-based catalysts for ammonia synthesis," said Prof. CHEN.