Effect of β-Li3N phase, Li2O addition and thermal treatment on the hydrogen sorption behavior of Li3N

The hydriding of Li3N to LiNH2 is investigated to clarify the influence of the beta-Li3N phase, the addition of Li2O and the thermal treatment of Li3N on the hydrogen storage properties of the Li-N-H system. As-milled Li3N displays fast initial absorption that is attributed to the formation of beta-Li3N nanograins, the increase of the surface area, and the presence of surface defects induced by mechanical milling. However, further hydrogen absorption is retarded in comparison with the as-received sample due to the presence of the beta-Li3N phase formed during milling. Thus, commercial Li3N exhibits the highest hydrogen storage capacity in the first cycle in comparison with as-heated Li3N and as-milled samples. In the case of Li2O addition, no interaction with Li3N was detected. The addition of LiH to the commercial Li3N. as-milled Li3N and Li3N-Li2O influences only the stability of the samples under hydrogen cycling. The hydrogen absorption/desorption behavior is mainly controlled by the amount of beta-Li3N formed during milling, while at long times the microstructure has a minor effect. (C) 2011 Elsevier B.V. All rights reserved.