Effect of the heat pretreatment of Li3N on its H2 storage performance

A comparison between the hydrogen storage performances of untreated and heat-treated Li3N was carried out using a volumetric method, temperature-programmed hydrogenation (TPH), and scanning electron microscopy (SEM). It was found that, during the first hydrogenation, the untreated Li3N could absorb fast (3 min), 5.5 wt % of hydrogen at 230 degreesC, and that 3200 min was needed to absorb an additional 2.5 wt % of H-2. In contrast, the Li3N preheated at 400 degreesC in a vacuum for 4.5 h absorbed only 3 wt % in 3 min at 230 degreesC but required only 300 min to absorb an additional 6.5 wt % of H-2. Furthermore, during rehydrogenation after desorption, the pretreated Li3N could quickly absorb (3 min) 5.2 wt % of hydrogen, and this performance did not change with increasing hydrogenation-dehydrogenation cycle number. TPH and SEM investigations indicated that the higher performance of the preheated Li3N was due to its relatively large particle sizes.