## 3 Results and Discussion
### Desorption Kinetics Using Sievert's Type Measurements
However, the enhanced kinetics due to Ni addition is considered to be associated with the increased heterogeneous sites for the nucleation of the complex hydride phases given in Equation (4). Additionally, Ni addition can facilitate the hydrogen diffusion through the complex hydride matrix [56]. Figure 6: Absorption kinetics of 2 LiNH\({}_{2}\)-nanoMgH\({}_{2}\) + 2 wt. % Ni and the base material 2 LiNH\({}_{2}\)-MgH\({}_{2}\) at 180, 200, and 220 \({}^{\circ}\)C [54]. X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) Scanning Electron Microscopy (SEM), and Energy Dispersive X-rays (EDX)  
The conversion or yield of the products have been determined by metrological characterization tools such as X-ray diffraction for phase identification, FTIR spectroscopic analysis for chemical bonding information, and SEM/EDX microscopic tools to evaluate the microstructure and nanoparticle size determination in addition to compositional (elemental) distributions. X-ray diffraction and Fourier transform infrared spectroscopy were employed to characterize the 2 LiNH\({}_{2}\)-MgH\({}_{2}\) compound after ball milling (BM), and after pressure composition temperature (PCT) measurements in hydrogenated/dehydrogenated conditions, to verify the validity of the reaction mechanism given in reaction (3). FTIR spectra of LiNH\({}_{2}\), 2 LiNH\({}_{2}\)-MgH\({}_{2}\) after 5 h ball milling (BM) and after PCT measurements in hydrogenated/dehydrogenated conditions are given in Figure 7. The characteristics of N-H asymmetric and symmetric vibrations of LiNH\({}_{2}\) at 3313 and 3259 cm\({}^{-1}\), respectively, were observed in 2 LiNH\({}_{2}\)-MgH\({}_{2}\) after 5 h BM. FTIR spectrum of hydrogenated 2 LiNH\({}_{2}\)-MgH\({}_{2}\) showed the characteristic bands of Mg(NH\({}_{2}\))\({}_{2}\) at 3278 and 3325 cm\({}^{-1}\) and Mg\({}_{3}\)N\({}_{2}\) band at 3160 cm\({}^{-1}\)[10; 57]. On the other hand, the FTIR spectrum of the fully dehydrogenated 2 LiNH\({}_{2}\)-MgH\({}_{2}\) showed the characteristic peaks of Li\({}_{2}\)Mg(NH)\({}_{2}\) compound at 3163 and 3180 cm\({}^{-1}\)[38]. The XRD profiles of the empty sample holder, 2 LiNH\({}_{2}\)-MgH\({}_{2}\) after 5 h BM and after PCT measurements in hydrogenated/dehydrogenated conditions, are given in Figure 8. Self-decomposition of Mg(NH\({}_{2}\))\({}_{2}\) to Mg\({}_{3}\)N\({}_{2}\) at elevated temperatures was discussed by [PERSON] et al., and further proved unambiguously by XRD and FTIR measurements in this study [41]. However, the XRD of the dehydrogenated sample resulted in an unidentified peak around 27.5\({}^{\circ}\) which needs to be further investigated. This peak could be the result of an oxide formation at high desorption temperatures due to the impurities in the as-received raw materials. The SEM/EDX mapping and image of the of 2 LiNH\({}_{2}\)-MgH\({}_{2}\) + 2 wt. % Ni is given in Figure 9, which clearly shows the uniform dispersion of nanoNi particles among the 2 LiNH\({}_{2}\)-MgH\({}_{2}\) compound. Therefore, 15 min is a reasonable duration for mixing catalyst with the base material. Moreover, the EDX spectral analysis of these samples demonstrated the correct 2 wt. % fraction of elemental Ni catalyst on a base hydride matrix. Additionally, the morphology and particles size of the nanoNi (obtained from QuantumSphere Inc.) catalyst was determined by the transmission electron microscopy (TEM), and is shown in Figure 10. From the TEM microstructure, it is evidenced that we have used cluster sizes of 3-10 nm nickel nanoparticles admixed with the base hydride compound that has enhanced hydrogen absorption and desorption kinetics. Figure 7: Fourier transform infrared spectroscopy (FTIR) spectra of LiNH\({}_{2}\)-nanoMgH\({}_{2}\) (2:1) before and after pressure composition temperature (PCT). Figure 8: X-ray diffraction (XRD) spectra of LiNH\({}_{2}\)-nanoMgH\({}_{2}\) after ball milling and after PCT measurements in hydrogenated/dehydrogenated states.