Impregnation method for the synthesis of Li-N-H systems

We demonstrated the feasibility of an impregnation method for the synthesis of Li₂NH (Li-imide) and LiNH₂ (Li-amide) for application as novel candidates for hydrogen storage materials. A metallic Li foil placed on a Ni foam was heated under Ar atmosphere and then impregnated homogeneously into the Ni foam without changing the bulk morphology of the foam. The morphology of the foam was retained after nitrogenation of the impregnated Li (formation of Li₃N) as well as after ten repeated hydrogenation and dehydrogenation reactions (reversible formation of Li₂NH and LiNH₂). It was noted that the hydrogenation reaction after the nitrogenation was drastically promoted by the addition of a small amount of Co powder on the metallic Li foil prior to the impregnation. Therefore, it is found that the impregnation method is useful to handle the Li-N-H systems as hydrogen storage materials because the bulk morphology is retained.