The Gore company, famous for "Goretex" makes hydrogen permeable membranes under the trademark "Primea". This membrane is effective for the purpose, but expensive.
http://www.gore.com/en_xx/products/electronic/fuelcells/series_56_mea_fuel_cells.html There is a much simpler, less costly solution for separating "most" of the hydrogen from "common manifold" gases in (claimed) ultra-efficient electrolysis, or BG/Meyer types of water-splitting. It is clear that the best, if not the only, possibility for greatly surpassing Faradaic limitations in water-splitting involves creating common manifold (mixed O2 and H2) gases, with all of the inherent risks. This is often called Brown's Gas (BG). ...but the major problem with verification: that is, that the large amounts of BG which come from such cells, is indeed mostly H2 and O2 and *not* mostly water-vapor... is to measure its actual heat content when burned. Unfortunately, without a decent level of separation of H2, prior to a flame, this is a dangerous proposition. However, almost any tightly woven fabric - the ones classified as "non-breathable" will preferentially pass H2 due to its much higher mobility and smaller molecular size. H2 permeates through extremely tight fabric weave as if it were no more than an open screen, whereas most of the O2 can be blocked, to the degree that the fabric is "non-breathable." It would seem that such an optimized tightly woven fabric, stretched as a "drumhead" over any common manifold electrolysis cell, would be greatly effective in changing the ratio of mixed gases away from stoichiometric levels of flamability. This need not be a super-high purity separation to be effective for an intended purpose ... but, as simple as this expedient sounds- it is somewhat of a wonder that no one claiming ultra-efficient electrolysis, seems to be doing it... Perhaps the various Meyer proponents (Ravi, etc) and the multitude of over-inflated claims, which are to be found on PESN: http://pesn.com/2007/08/31/9500496_Ravi_waterfuelcell_suppression/ ...do not want to find out the truth about what their cells are really producing ? After all, how hard is it to fabricate such a drumhead? I suspect that it is almost, but not quite, as easy as fabricating a tall-tale of nebulous "suppression". The intended purpose of such a drumhead arrangement, of course, would be to provide a simple and safe protocol for safely porting (mostly) H2 to a flame with little risk of blowback to the cell. IMHO, a drumhead separator can be combined with a "bubbler" to provide a *high level* of safety without the need for drying, or secondary pressurization. You may lose 1-2% of the H2, since the (mostly) O2 should be vented and discarded (it could still be dangerous)- and not be used to burn the H2 with - but so what? - if your claim of extreme OU is valid, then a few percent loss of H2 in the vented O2, and also having the (mostly) H2 gas flow burned in air instead of O2, is not going to make a major difference in the heat output which is seen. Jones
