Acknowledgements

Mð Þ<sup>s</sup> þ H2 gð Þ ⇆ MH2 sð Þ (23)

, (25)

ΔH<sup>0</sup> ¼ ΔH þ ½ð � 3Vm Eð Þ γ;r; Eads =r (24)

� <sup>Δ</sup><sup>S</sup> R 

lnPeq <sup>¼</sup> <sup>Δ</sup>H<sup>0</sup>

Gold Nanoparticles - Reaching New Heights

[94–96].

5. Conclusions

by developing new ones.

148

RT 

Nanoconfinement was basically proposed as a promising strategy to make hydride compounds reversible under mild conditions, as for example LiBH4, NaAlH4, and MgH2, and to further destabilized hydrogen systems such as

2LiBH4 + MgH2. However, in most of the cases, the main effect was observed on the kinetic behavior of the hydride compounds and systems. The nanometric range of the particles provide extremely large grain boundaries and notable shorter diffusion paths as well as optimized contacting for the materials, hence these properties account for improvements in terms of kinetic behavior and cycling stability. Carbon frames such as scaffolds, nanotubes, and aerogels are used for confining hydrides due to its light weight and inter condition. Despite the fact that this strategy usually leads to improved kinetic behavior without actually changing the thermodynamics of the hydride compound and system, the main constraint lay on the reduced capacity because of the introduction of the hydride into the nanoporous frame. Furthermore, it is hard to figure out in a possible scale-up for practical application

Hydrogen can be considered as future energy carrier because of its large gravimetric energy density, abundance as combined with oxygen in water and its environmentally friendly condition at the time to release its energy. However, its low volumetric energy density owing to its gas conditions demands an efficient and a safe method to store hydrogen. One of the most attractive methods consists in storing hydrogen in solid state by forming a hydride compound. Much effort has been put in designing hydride forming materials and hydrogen storage systems based on hydride forming materials. One of the main constraints for the design of commercial solid-state hydrogen storage systems is the lack of a hydride forming material able to have proper thermodynamic stability as well as kinetic behavior. There are already materials with suitable experimental thermodynamic properties which would allow to reversibly uptake and release hydrogen at low temperature of about 90°C and under low pressures. Nonetheless, these conditions predicted by the thermodynamics of the system cannot be reached because of kinetic constraints. Therefore, strategies to tailor the kinetic behavior of hydride compounds and system of technical interest have been intensively developed. In this chapter, all the basics concepts about the chemical reaction, thermodynamics and kinetics for the right understanding of the solid-state hydrogen storage as hydride compounds or systems were explained. Then, the main strategies to tune the kinetic behavior of hydride compounds or systems were described. Among the most interesting strategies, milling process, transition metal, and transition metal compound doping, in situ catalyst formation and nanoconfinement were developed. Despite the fact that several hydrogen storage materials were notably improves by applying the exposed strategies, none of the materials nowadays fulfills the requirements for an efficient, a safe, and a cost effective practical application; hence, there is the need for further research in this field by applying the traditional design strategies and/or

The author acknowledges CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas) and Alexander von Humboldt Foundation (Fellowship Number: ARG-1187279-GF-P).
