Hydrogen desorption/absorption properties of Li–Ca–N–H system

Abstract

Hydrogen storage properties of two ball-milled composites of Ca(NH 2 ) 2 + 2LiH and CaH 2 + 2LiNH 2 were investigated as a series of searching studies of high performance hydrogen storage materials. About 4.5 mass% hydrogen is desorbed from about 100 • C and the thermal desorption profiles show a peak around 200 and 220 • C for the composites of CaH 2 + 2LiNH 2 and Ca(NH 2 ) 2 + 2LiH, respectively, under a helium flow at 5 • C/min heating rate without any NH 3 emission within our experimental accuracy. The powder X-ray diffraction and infrared absorption spectroscopy indicated that the dehydrogenated states of both composites form "an unknown imide phase" after heating up to 400 • C, while the dehydrogenated states after heating up to 200 • C in vacuum are the mixed phases of Li 2 NH and CaNH. The rehydrogenated state for the ball-milled composite of CaH 2 + 2LiNH 2 is transformed into the composite of Ca(NH 2 ) 2 and 2LiH by repeating the dehydrogenation and rehydrogenation cycles at 180-200 • C.

Evaluation of the enthalpy change due to hydrogen desorption for M–N–H (M = Li, Mg, Ca) systems by differential scanning calorimetry

“…Especially of note is that the reaction product Li 2 NH has a very complicated crystal structure [40e42], which is not refined yet, and thus, it might strongly influence the theoretical estimations. The hydrogen desorption reaction of LieCaeNeH systems (c) and (d) in this temperature range are expressed as follows [28]:…”

“…The milling was performed for 10 h at room temperature by using a planetary ball mill (Fritsch P-5) at 250 rpm. Detailed sample preparations of the mixture of LiNH 2 eLiH with 1 mol% TiCl 3 , 3 Mg(NH 2 ) 2 e8LiH, Ca(NH 2 ) 2 e2LiH, and 2LiNH 2 eCaH 2 were described in our previous papers [17,23,28]. All of the samples were handled in a glove box filled with purified Ar (DBO-1NKH, Miwa Mfg.…”

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

“…The operating temperature of Li-N-H can be reduced by modifying the thermodynamic properties of the system, and, in this context, the substitution of LiH with other metal hydrides represents one of the strategy widely adopted in the recent past [40][41][42][43][44][45][46]. Among the most relevant results, it is worth to highlight that the combination of LiNH 2 and LiBH 4 (2:1) lead to the desorption of a significant amount of hydrogen, around 10 wt.…”

Thermal Dehydrogenation Characteristics of Li-Sr-Al-N-H Hydrogen Storage System

“…In addition, growing attention has also been paid to the metal-N-H systems as hydrogen storage materials in the last decade [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] . Chen et al first reported that the binary LiNH 2 -LiH (1:2) system exhibits reversible de-/hydrogenation reactions in a two-step process, which can be expressed as 10 :…”