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

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 1H and 6Li nuclear magic angle spinning (MAS) magnetic resonance (NMR) spectroscopy from ambient temperature to 180 °C. Up-field chemical shift was observed in 6Li MAS NMR spectra with increased milling time, indicating that average local electronic structure around Li nuclei was modified during MA. 1H MAS NMR was used to dynamically probe ammonia release from the activated LiNH2 at temperature as low as 50 °C. In the case of activated LiH + LiNH2 mixtures, the 1H MAS NMR results implied that MA enhanced the dehydrogenation reaction of LiNH2 + LiH = Li2NH + H2.