Among many complex hydrides investigated, some of the amides (i.e., LiNH\({}_{2}\)/Mg(NH\({}_{2}\))\({}_{2}\)) had shown favorable storage capacity and reversibility. The studies on the interaction of lithium with hydrogen and nitrogen as early as 1910 led to the discovery of the LiNH\({}_{2}\)-LiH system [2; 3]. However, a detailed investigation of this system as a potential hydrogen storage material was not carried out until 2002 when [PERSON] et al. [4] first reported the promising results for the lithium nitride (Li\({}_{3}\)N) system, in which reaction consists of two steps and given as:  
\[\mathrm{Li_{3}N+2H_{2}\leftrightarrow Li_{2}NH+LiH+H_{2}\leftrightarrow LiNH_{2}+ LiH} \tag{1}\]  
The theoretical capacity of Li\({}_{3}\)N system is 10.4 wt. %; however, only the second step of the reaction path given in (1) is practical for reversible hydrogen storage since the first reaction step has a very low equilibrium pressure (\(\sim\)0.07 bar) [4]. Further investigation of the second step of the reaction (1), which has a theoretical capacity of 6.5 wt. % and favorable thermodynamics, revealed the role of the lithium hydride (LiH). The elementary steps are given by the reaction steps (2) and (3) as follows [5]. \[\mathrm{2 LiNH_{2}\to Li_{2}NH+NH_{3}} \tag{2}\]  
\[\mathrm{NH_{3}+LiH\to LiNH_{2}+H_{2}} \tag{3}\]  
The reaction (3) was found to be ultrafast (\(\sim\)25 ms) and responsible for the capture of NH\({}_{3}\) which is detrimental for the fuel cells [5]. After these prolific works, the research on hydrogen storage in amides focused on compositional changes, replacement of Li with other light or more electronegative alkali/earth alkaline metals, mechanical activation, effects of catalysts, reaction mechanism, reversibility issues, and the mitigation of NH\({}_{3}\) emission. The high desorption temperature (\(\sim\)285 \({}^{\circ}\)C at 1 bar) of the LiNH\({}_{2}\) + LiH system, which is not feasible for mobile applications, led to studies on the destabilization of the system. One of the ways involves replacing Li with more electronegative metals such as Mg, Na, and Ca. [PERSON] et al., partially replaced Li in LiNH\({}_{2}\) with 90 at. % Li and 10 at. % Mg, and obtained a 50 K reduction in the desorption temperature [6]. Later, [PERSON] developed a new hydrogen storage material by completely replacing LiH with MgH\({}_{2}\) in the reaction (1). The resulting compound had a 4.5 wt. % gravimetric capacity with a plateau pressure of 30 bar at 200 \({}^{\circ}\)C [7]. Further studies on the LiNH\({}_{2}\)-MgH\({}_{2}\) system concentrated on the reaction mechanism, kinetics, structural characterization, and thermodynamics of the system [8; 9; 10; 11; 12; 13; 14; 15; 16; 17]. It was shown that the 2 LiNH\({}_{2}\)-MgH\({}_{2}\) system transforms into the Mg(NH\({}_{2}\))\({}_{2}\)-2 LiH system after the first desorption/absorption cycle, and the proposed reaction mechanism is [8; 9]:  
\[\mathrm{MgH_{2}+2 LiNH_{2}\to Li_{2}Mg(NH)_{2}+2H_{2}\leftrightarrow[Mg(NH_{2}) _{2}]+2 LiH} \tag{4}\]  
The different compositions of the Li-Mg-N-H system were also investigated. [PERSON] et al. obtained \(\sim\)7 wt. % capacity with a 3 Mg(NH\({}_{2}\))\({}_{2}\)-8 LiH compound, and [PERSON] et al. investigated a 3 Mg(NH\({}_{2}\))\({}_{2}\)-12 LiH compound with a capacity of 9.1 wt. % [18; 19; 20]. Despite the higher gravimetric capacities of these systems, desorption temperatures were relatively higher than the Mg(NH\({}_{2}\))\({}_{2}\)-2 LiH compound. [PERSON] et al. examined the LiH-Mg(NH\({}_{2}\))\({}_{2}\) with molar ratios of 1:1, 2:1 and 3:1, and showed that the lower the Li content the higher the NH\({}_{3}\) emission, and the higher the Li content the higher the desorption temperature [21]. A LiNH\({}_{2}\)-MgH\({}_{2}\) (1:1) compound was also investigated by several researchers, and the results showed considerable NH\({}_{3}\) emission, and the revealed reaction mechanism was quite different than the LiNH\({}_{2}\)-MgH\({}_{2}\) (2:1) compound [13; 22; 23].