Q.How do you expect the metallic hydrides to be useful for hydrogen storage? Explain.

Certain transition metals and alloys (e.g., Pd, Ti, Ni, LaNi5, FeTi) can absorb very large volumes of dihydrogen gas into the interstitial spaces of their crystal lattice, forming metallic (interstitial) hydrides:

This process is reversible: on mild heating (or lowering pressure), the metal releases the absorbed hydrogen gas again, regenerating the parent metal.

Usefulness for hydrogen storage:

• A given volume of metal can hold a surprisingly large amount of hydrogen — often more densely than the same volume of compressed or even liquid H2 — making storage compact.
• Storing H2 chemically bound within a solid metal lattice is much safer than storing it as a highly compressed gas (high pressure hazard) or cryogenic liquid (very low temperature, boil-off losses). …

Recall that transition metals form interstitial hydrides by absorbing H2 into lattice voids, and that this absorption is reversible on heating — reason from …

• Confusing metallic/interstitial hydrides with ionic (saline) hydrides — only the former show this reversible gas-absorption behaviour useful for storage. …