Amorphous LiNxHy Boosts Low-Temperature Ammonia Decomposition over the Co/MgO Catalyst

Catalytic ammonia decomposition facilitated by lithium species such as LiNH₂ and Li₂NH has attracted increasing attention alongside growing interest in hydrogen energy. However, the active site requirements and reaction mechanisms of Li-assisted catalysts remain controversial. In this study, we demonstrate that the incorporation of lithium species significantly enhances the ammonia decomposition rate of a cobalt-based catalyst by up to 5-fold at 623 K and achieves almost the best low-temperature activity among reported Ru-free catalysts. Structural characterization and density functional theory (DFT) calculations suggest that Li sites with vacancies, located at the interface between the amorphous LiN_xH_y species and the Co surface, serve as the active sites for ammonia decomposition. For the N–H bond scission step during ammonia cracking, Li atoms located at this vacancy site exhibit a displacement of 1.7 Å per Li atom under a direct weak interaction with the Co surface to construct the energy-favorable geometry.