Single-Atom Barium Promoter Enormously Enhanced Non-Noble Metal Catalyst for Ammonia Decomposition

As a well-established topic, single-atom catalyst has drawn growing interest for its high utilization of metal. However, researchers prefer to develop various active metals with single-atom form, the intrinsic roles of single-atom promoters are usually underrated, which are significant in boosting reaction activity. In this work, Ba single atoms were in situ prepared in the Co-Ba/Y₂O₃ catalyst with crystallized BaCO₃ as the precursor under the ammonia decomposition reaction condition. The optimized Co-Ba/Y₂O₃ catalyst achieves extremely high H₂ production rate of 138.3 mmolH₂ ⋅ g_cat ^-1 ⋅ min^-1 at very low temperature (500 °C, GHSV=840,000 mL ⋅ g^-1 ⋅ h^-1) and Co-Ba/Y₂O₃ exhibits excellent durability during the 350 h test, which realizes the highest activity among all non-noble catalysts, and reaches or even exceeds numerous reported Ru-based catalysts. Both Y₂O₃ and Co demonstrate positive interactions with Ba, which significantly facilitates the dispersion of Ba species at high temperatures (≥600 °C). Ba single atoms significantly enhance the charge density of Co and form additionally active Co-O-Ba-Y₂O₃ interfacial sites, which alleviates hydrogen poisoning and decreases the reaction barrier of the N-H bond activation of *NH. The exploration of atomically dispersed promoters is groundbreaking in heterogeneous catalysis, which opens up a whole new domain of catalytic material.