Effect of Pore Confinement of LiNH₂ on Ammonia Decomposition Catalysis and the Storage of Hydrogen and Ammonia

LiNH₂ is of interest to several aspects of energy storage such as reversible hydrogen storage, battery technology, catalysis, and ammonia capture/storage. We investigated the impact of nanoconfinement in carbon scaffolds on the hydrogen and ammonia release properties of LiNH₂ and its catalytic activity in NH₃ decomposition. Ammonia release from macrocrystalline LiNH₂ begins at 350°C, while confined LiNH₂ releases ammonia from below 100°C under helium flow. This ammonia release consisted of 30.5 wt % ammonia in the first cycle and was found to be partially reversible. Above 300°C, hydrogen is also released due to an irreversible reaction between LiNH₂ and the carbon support to form Li₂NCN. Ni-doped LiNH₂/C nanocomposites were active in the catalytic decomposition of ammonia into N₂ and H₂ with 53% conversion at 400°C and a gas hourly space velocity of 13000 h^-1. This is comparable to the performance of a commercial-type Ru-based catalyst where 79% conversion is observed under the same conditions. This work demonstrates that nanoconfinement is effective for improving the functionality of LiNH₂. The versatility of this system offers promise in a number of different areas including hydrogen/ammonia storage and ammonia decomposition catalysis. (Chemical Equation Presented).