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The most common element in the universe is hydrogen. With its growing potential use in fuel cells and elsewhere, efficient means of separating the gas is needed. |
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 The discovery of palladium’s remarkable ability to absorb hydrogen have since lead to uses which take advantage of this affinity. As a thin membrane, palladium will allow hydrogen to permeate through the membrane, but block all other gases. The further discovery of the stability of palladium-silver alloys and the ability to manufacture membranes of these alloys made hydrogen purification using palladium–silver membranes possible.
The mechanism of hydrogen involves a series of steps:
1) adsorption
2) dissociation
3) ionization
4) diffusion
5) reassociation
6) desorption
Several molecules of hydrogen and nitrogen atoms are on the metal surface. Within the metal, hydrogen loses its electron to the palladium structure and diffuses through the membrane as an ion (or proton). At the exit surface the reverse process occurs.
Palladium-silver membrane based hydrogen purification is used in many applications including semiconductor manufacturing. In particular, these membranes have wide spread use in the compound semiconductor industry, where the absolute purification of hydrogen is critical. When coupled with an effective purge system, a palladium-silver membrane based hydrogen purifier will give years of reliable service.
For the purification and/or separation of hydrogen from gas mixtures, the palladium alloy system offers a number of attractive features; the foremost of these is the quality of the ultra pure hydrogen itself. The diffusion cells involve no moving parts and the intrinsic value of the noble metal represents a recoverable investment.
Source: Johnson Matthey |
