NH₃ Mediated or Ion Migration Reaction: The Case Study on Halide–Amide System

Lively debates on hydrogen desorption from the amide–hydride system via either ion migration or NH₃ mediated mechanisms have been ongoing since the discovery of the amide–hydride system for hydrogen storage. In this work, we employed kinetic analyses to demonstrate that the mechanism of hydrogen desorption depends on the sample morphology and desorption conditions. Upon the formation of Li amide bromide (Li₂NH₂Br), the LiNH₂ unit is confined in the cage of Br, resulting in less mobility of ion. Hydrogen desorption from the Li₂NH₂Br–2LiH system appears to follow the NH₃ mediated mechanism even if the two starting chemicals have been intensively ball milled. On the other hand, the migrations of Li⁺ and H⁺ play important roles leading to H₂ formation from the direct combination of H⁺ (from −NH₂) and H^– (from LiH) when LiNH₂ and LiH are intimately in contact.