Design of Alkaline Earth-Doped Co/MgO Catalysts for Ammonia Decomposition

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_0.01Mg_0.99O 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_0.01Mg_0.99O 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 N₂ 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.