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

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journal contribution
posted on 2014-02-06, 00:00 authored by Hujun Cao, Jianhui Wang, Yongshen Chua, Han Wang, Guotao Wu, Zhitao Xiong, Jieshan Qiu, Ping Chen
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.