[WulfKeeper]

G’day all, I’m a forum n00b and should confess up front that I’m an astrophysicists. However, my knowledge of chemistry is very much at the undergrad level so I beg the indulgence of the great collective chemical minds 

Regarding hydrogen and its isotopes, if I understand correctly then they can be mechanically pushed through solid palladium metal sheet. No external electrical input required. Put the gas under pressure (10’s of kPa gauge) on one side of the metal, the other side under vacuum (10’s of Torr) and the hydrogen will pass through the metal.

When put to me for explanation it struck me as obviously some kind of magic and I started investigating further 

I did some reading and it seems the mechanism relies on chemical dissociation of the diatomic (H2/D2) gas species at the surface of the Pd. This breaks the diatomic bond and allows the atomic H or D (or has it now been ionised H+/D+?) to squeeze through the metal’s internal lattice structure.

Can someone please explain to me at an undergrad level how this dissociation occurs? What is it about the H2/D2 getting pushed up against the surface of the Pd that makes the metal more attractive than its fellow atom in the diatomic molecular form? (Why will that break the bond in favour of entering the metal?) Or have I completely misunderstood what’s happening?

Any suggestions of further (undergrad) reading material on the topic would be gratefully accepted. I’m reasonably comfortable with topics like orbital probability and valency. The material I’ve found on surface dissociation to date however is way over my head 

Kind regards
W

[Borek]

http://en.wikipedia.org/wiki/Palladium_hydride contains a link to this paper: http://prl.aps.org/abstract/PRL/v93/i14/e146103

It is probably more than you are asking for.