Adsorption of hydrogen by palladium

[verdigris]

How does hydrogen gas get into a piece of palladium metal such that the amount of hydrogen is 900 times the volume of palladium?A strong pump would be required to put 900 times the volume of a gas cylinder into the cylinder or the hydrogen would have to have its temperature lowered first.
Heat is evolved as hydrogen goes into the palladium - is this the hydrogen being cooled or pd-h bonds forming?

 

[haiha]

I do not if there's any Pd-H bond formed when H2 comes into palladium, but part of the heat is due to the entropy following the term : T*deltaS.
Volume is reduced and so is entropy.