Dehydriding reaction

Aoki, M. Noritake, T. Kitahara, G. Nakamori, Y. Towata, S. Orimo, S., Dehydriding reaction of Mg(NH2)2-LiH system under hydrogen pressure. Journal of Alloys and Compounds 2006,428, (1-2), 307-311. 

They found that the amounts of the hydrogen desorbed from the mixtures with = 6, 8, and 12 on a unit mass basis slightly decreased with increasing n ( 5.4, 5.1 and 4.5 wt%, respectively). However, the molar ratios of the desorbed hydrogen to the mixtures were almost equal and the PCT isotherms were similar to each other. The plateau pressure for desorption of the (3Mg(NH2)2 + 12LiH) mixture was equal to 8-10 MPa, 3.5 MPa and 2 MPa at 250°C, 225 and 200°C, respectively. The desorption/absorption PCT curve at 250°C exhibited only very small hysteresis which means that the plateau pressures at this temperature are nearly identical. The Li Mg(NH)2 and LiH phases were observed in XRD profiles of all the mixtures after PCT measurements. These results suggest that the dehydriding reaction of the... 

S. Orimo, Y. Nakamori, G. Kitahara, K. Miwa, N. Ohba, T. Noritake, S. Towata, Destabilization and enhanced dehydriding reaction of LiNH2 an electronic structure viewpoint , Appl. Phys. A 79 (2004) 1765-1767. 

It is known that the electrochemical hydriding/ dehydriding reactions taking place at a hydrogen storage electrode in an alkaline solution may be simply expressed as follows ... 

Figure 2 shows the strong dependence of temperature on the plateau pressure. The higher the temperature, the higher is the plateau pressure. This is an important thermodynamic consequence of the heat of reaction Ah associated with Eq. 1. The hydriding reaction (->) is exothermic and the dehydriding reaction ( -) is endothermic. The plateau pressure Pp is related to the absolute temperature T by the Van t Hoff equation... 

The enthalpy values of dehydriding AIH3 have been determined. The a-phase dehydriding reaction was found to be endothermic with 6.0 1.5kJ (molH2) consistent with values reported elsewhere of 7.6kJ (molH2) [19]. Similar to early reports, the y-phase showed exothermic transformation to the a-phase followed by dehydriding to aluminum with a net endothermic heat of reaction of 1.0 0.5kJ (molH2). The P-phase, however, was found to dehydride directly to aluminum, which is a different result from results reported elsewhere [15, 16, 19]. 

AHd Is the enthalpy change of the dehydriding reaction. Calculated value. The others are experimental values. 

Nakamori Y, Ninomiya A, Kitahara G, Aoki M, Noritake T, Miwa K, Kojima Y and Orimo S (2006), Dehydriding reactions of mixed complex hydrides, J. Power Sources, 155, 447 55. 

During the initial dehydriding reaction of NaAlH4, seen in equation 1, NaAlH4 rapidly evolves... 

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