Explain about Hydrogen sponge.

Explanation

(i) Hydrogen sponge (or) metal hydride E.g. palladium hydrogen system is a binary hydrid (PdH)
(ii) Upon heating, H atoms diffuse through the metal to the surface and recombine to from molecular hydrogen. Since no other gases behaves this way with palladium, this process has been used to separate hydrogen gas from other gas
`2Pd_((s))+H_(2(g)) (iii) The hydrogen molecule readily absorb on palladium surface, where it dissociates into atomic hydrogen. The dissociated atoms dissolve into the interstices or voids of the crystal lattice

(iv) Technically the formation of metal hydride is by chemical reaction but it behaves likes a physical storage method.