Hydrogen is expected to be used as a fuel additive to ammonia, a non‐flammable and carbon‐free fuel, to improve combustion efficiency. However, the design strategies for developing highly active, nonprecious metal catalysts for ammonia decomposition are not yet well understood. Here, we show that Co/Ba 0.01 Mg 0.99 O exhibits high activity, with an ammonia conversion of 94.4% and a hydrogen production rate of 3.79 mol g cat −1 h −1 at 500°C with a WHSV of 60,000 mL g cat −1 h −1 . Comparison of the dopant effects of alkaline earth metal elements elucidates that the high activity of Co/Ba 0.01 Mg 0.99 O is ascribed to the formation of a specific Co‐BaO core–shell‐like structure, with highly basic BaO nanoparticles covering the Co particles. The core–shell‐like structures were not formed with other alkaline earth elements. Such features facilitate efficient electron donation to Co nanoparticles, promoting N 2 formation. Furthermore, kinetic analysis indicated that doping of alkaline earth metals weakens the adsorption of strongly bound species. Our findings will contribute to the development of cost‐effective supported metal catalysts for hydrogen production through ammonia decomposition, leading to the realization of a carbon‐neutral society in which ammonia plays a key role.
Hayashi et al. (2026) studied this question.