Study the effects of mechanical activation on Li-N-H systems with H-1 and Li-6 solid-state NMR

Abstract

To gain insight into the effects of mechanical activation (MA) on the hydrogen desorption of the lithium amide (LiNH2) and lithium hydride (LiH) mixture. LiNH2 and LiH + LiNH2 were mechanically activated by high-energy ball milling. The formed products were studied with in situ H-1 and Li-6 nuclear magic angle spinning (MAS) magnetic resonance (NMR) spectroscopy from ambient temperature to 180 degrees C. Up-field chemical shift was observed in Li-6 MAS NMR spectra with increased milling time, indicating that average local electronic structure around Li nuclei was modified during MA. H-1 MAS NMR was used to dynamically probe ammonia release from the activated LiNH2 at temperature as low as 50 degrees C. In the case of activated LiH + LiNH2 mixtures, the H-1 MAS NMR results implied that MA enhanced the dehydrogenation reaction of LiNH2 + LiH = Li2NH + H-2. (c) 2007 Elsevier B.V All rights reserved