Activation of hydrogen storage materials in the Li-Mg-N-H system: Effect on storage properties

摘要

We investigate the thermodynamics, kinetics, and capacity of the hydrogen storage reaction: Li_2Mg(NH)_2 + 2H_2 mutually impiles Mg(NH_2)_2 + 2LiH. Starting with LiNH_2 and MgH_2, two distinct procedures have been previously proposed for activating samples to induce the reversible storage reaction. We clarify here the impact of these two activation procedures on the resulting capacity for the Li-Mg-N-H reaction. Additionally, we measure the temperature-dependent kinetic absorption data for this hydrogen storage system. Finally, our experiments confirm the previously reported formation enthalpy (triangle open H), hydrogen capacity, and pressure-composition-isotherm (PCI) data, and suggest that this system represents a kinetically (but not thermodynamically) limited system for vehicular on-board storage applications.