Enhanced Hydrogen Storage Properties of Li−Mg−N−H System Prepared by Reacting Mg(NH2)2 with Li3N

Abstract

The Li−Mg−N−H system was prepared by reacting magnesium amide [Mg(NH2)2] with lithium nitride (Li3N) and investigated with regard to the hydrogen storage properties. Our study shows that the present method is superior to the conventional route in enhancing the reversible dehydrogenation properties. Through optimizing the Li3N:Mg(NH2)2 ratio in the starting materials, the reversible capacity of Li−Mg−N−H system increases to 4.9 wt %, 18% higher than that typically obtained from the Mg(NH2)2 + 2LiH mixture at 200 °C. Furthermore, increasing the Li3N:Mg(NH2)2 ratio is effective for mitigating the ammonia release from thus-prepared samples. Combined property/structure investigations indicate that the obtained enhancements should be ascribed to the effects of LiNH2 and LiH that were in situ generated from the excess Li3N. LiNH2 may promote the dehydrogenation reaction via seeding the reaction intermediate. The concurrently generated LiH acts as an effective ammonia trapping agent. These findings highlight the potential of “intermediate seeding” as a strategy to enhance the reversible hydrogen storage properties of metal−N−H systems.