Lithium nitride for reversible hydrogen storage

Abstract

In this paper, we examined the basic properties in the 1:1 mixture of lithium amide LiNH 2 and lithium hydride LiH as a candidate of reversible hydrogen storage materials.The thermal desorption mass spectra of the ball milled mixture without any catalysts indicated that hydrogen H 2 is released in temperature range from 180 to 400 ℃ with emitting a considerable amount of ammonia NH 3 . On the other hand, the ball milled mixture containing a small amount of TiCl 3 as a catalyst showed the most superior hydrogen storage properties among the 1:1 mixtures with a small amount of catalysts, Ni, Fe, Co metals and TiCl 3 (1 mol.%). That is, the product desorbs a large amount of hydrogen (~5.5 wt.%) in the temperature from 150 to 250 ℃ under the condition of a heating rate of 5 ℃/min, but it does not desorb ammonia at all within our experimental accuracy. In addition, we confirmed that the product shows an excellent cycle retention with an effective hydrogen capacity of more than 5 wt.% and a high reaction rate until at least 3 cycles.

Mechanisms for the decomposition and dehydrogenation of Li amide/imide

“…Others have proposed that NH 3 necessarily evolves as a transient gas and the dehydrogenation of LiNH 2 +LiH mixtures involves an intermediate step: [6][7][8][9][10][11][12][13] 2LiNH 2 → Li 2 NH + NH 3 ;…”

“…The decomposition of LiNH 2 into Li 2 NH and NH 3 is well known, 4,7,8 and it was Hu and Ruckenstein who pointed out that NH 3 reacts quickly with LiH. 6,7 The activation energy for the decomposition of LiNH 2 was estimated to be 2.53 eV (before ball milling), and it was found to decrease with increasing ball-milling time.…”

Correlation between kinetics and chemical bonding state of catalyst surface in catalyzed magnesium hydride

“…Many kinds of hydrogen absorbing materials have been studied in order to store hydrogen, such as sodium alanates [1], [2], metal nitrides [3], [4], as well as MgH 2 [5], [6], which is one candidate because of its high hydrogen capacity (7.6 mass%).…”

Recent Progress and New Perspectives on Metal Amide and Imide Systems for Solid-State Hydrogen Storage

“…Experimentally, in the temperature range of 180-400 • C this system desorbs hydrogen together with a large amount of ammonia, which should be avoided because it is the main responsible for the catalyst poisoning phenomenon in fuel cells [6][7][8]. Furthermore, it has been proved that the ammonia concentration brutally increases as the number of ab-desorption cycles increases, affecting the gravimetric capacity of the whole system [9].…”

“…%) is added to the system, almost the 80% of hydrogen is desorbed (5.5 wt. %) within 30 min at 200 • C and without ammonia release [7,11]. TiCl 3 acts as a catalyst favoring the transfer of ammonia to lithium hydride and thus improves the hydrogen desorption kinetics of the LiNH 2 -LiH system.…”