Alanates (i.e. NaAlH4 and LiAlH4) have been identified as the promising hydrogen storage candidates due to their high volumetric and gravimetric hydrogen densities. Extensive investigations have shown that the hydrogen kinetics and reversibility of NaAlH4 can be significantly enhanced upon the addition of catalysts. Unfortunately, the positive catalytic effects observed with NaAlH4 have been difficult to translate to LiAlH4 of a much higher hydrogen storage capacity. LiAlH4 also suffers from hydrogen thermodynamic constraints, and to date there is no clear path to effectively control the hydrogen storage properties of alanates. Nanosizing is believed to be an attractive alternative approach that could allow control over the hydrogen properties of complex hydrides. This thesis aimed at further understanding the potential of this approach and identify the significant hydrogen properties alterations occurring when alanates are nanosized. In this respect, particle size restriction was first implemented through the known method of hydrides confinement in mesoporous carbons. Through this learning, nanoconfined NaAlH4, LiAlH4, and KAlH4 all clearly demonstrated an improved hydrogen release and uptake behaviour, and this evidenced a clear correlation between particle size restriction and hydrogen properties across well-known alanates. From this learning, the focus had then been to translate the nanoconfinement approach to the freestanding alanate nanoparticles, where there is no dead weight from the scaffold to compromise the practical hydrogen storage capacity of alanates. Methods using both steric/electrostatic stabilisation had been established to effectively synthesise NaAlH4 and LiAlH4 nanoparticles. To enable hydrogen reversibility by keeping the decomposition products in close vicinity upon hydrogen release, method to enable the deposition of a titanium (Ti) metallic shell at the surface of the freestanding alanate particles had also been advanced. Hence, by forming a core(alanate)-shell(Ti) particles, the full storage hydrogen capacity of the material became accessible. More remarkably, through this nanosizing approach it became possible to shift and modify the thermodynamics of NaAlH4 and LiAlH4, their hydrogen release path, but also the position and shape of the equilibrium plateau pressure.