Al–N–H compounds derived from ammonia alane: Synthesis strategies and characterization
Résumé
Ammonia alane (AlH 3 NH 3 , AA) is a solid hydrogen carrier with a high gravimetric hydrogen storage capacity of 12.86 wt%. In this study, we present the first experimental investigation of Al-N-H compounds synthesized via three distinct routes: (i) Lewis acid-base reaction, (ii) metathesis, and (iii) cryo-milling. Characterization techniques including FTIR spectroscopy, thermal analysis, X-ray photoelectron spectroscopy, and solid-state 1 H and 27 Al MAS NMR spectroscopy revealed the coexistence of multiple aluminum environments. However, the successful formation of AA could not be confirmed. Ambient storage and mild thermal activation (at 80 • C) led to the formation of Al-N polymers, likely resulting from dehydrogenation and partial deammoniation, underscoring the thermal instability of these phases. These findings highlight the need for a rigorously controlled synthesis-tocharacterization workflow under inert and subzero conditions (below -45 • C) to enable the isolation, comprehensive characterization, and evaluation of pristine AA for solid-state reversible hydrogen storage applications.
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