Nanoconfined light metal hydrides for reversible hydrogen storage

Nano-sizing and scaffolding have emerged in the past decade as important strategies to control the kinetics, reversibility, and equilibrium pressure for hydrogen storage in light metal hydride systems. Reducing the size of metal hydrides to the nanometer range allows fast kinetics for both hydrogen release and subsequent uptake. Reversibility of the hydrogen release is impressively facilitated by nanoconfining the materials in a carbon or metal-organic framework scaffold, in particular for reactions involving multiple solid phases, such as the decomposition of LiBH4, NaBH4, and NaAlH4. More complex is the impact of nanoconfinement on phase equilibria. It is clear that equilibrium pressures, and even decomposition pathways, are changed. However, further experimental and computational studies are essential to understand the exact origins of these effects and to unravel the role of particle size, physical confinement, and interfaces. Nevertheless, it has become clear that nanoconfinement is a strong tool to change physicochemical properties of metal hydrides, which might not only be of relevance for hydrogen storage, but also for other applications such as rechargeable batteries.