Modification of the hydrogenstorage properties of Li3N by confinement into mesoporous carbons

Abstract

This study presents an innovative synthetic route to Li₃N@carbon composites for the purpose of use as hydrogen storage materials. The synthesis method is provided by wet impregnation of mesoporous carbons (graphitic or non-graphitic) using lithium azide solutions, followed by a thermal treatment allowing the transformation of lithium azide into lithium nitride, the latter being formed into the porosity of the carbon hosts. It has been shown by X-ray diffraction that the high-pressure β-phase of Li₃N can be stabilized within the carbon matrix. The resulting Li₃N@carbon composites have desirable hydrogen storage properties with fast hydrogen absorption/desorption kinetics at 200 °C (much faster than those measured for non-confined Li₃N) as well as a completely reversible hydrogen storage process: a 20 wt% Li₃N-loaded composite leads to a reversible hydrogen storage capacity of 1.8 wt% (e.g. about 9 wt% per mass of Li₃N).