I recently purchased a Nafion 117 membrane from FuelCellsEtc and tried to perform a chemical deposition of Pt and Au in the membrane. I have a diffusion cell to perform the deposition with the metal salt on one side and the borohydride on the other. Nafion is a cation exchanger and the metal cations should be readily pulled into the membrane while borohydride (my reducing agent) should only penetrate the membrane to a small extent, leaving a thin, porous network of metal in the membrane. However, the membrane I was sent is completely resistant to impregnation from the metal solution while readily allowing my reducing agent to pass through (metal is being deposited on the metal solution side of the membrane and falling off the membrane into solution.
Did they send me the wrong product? How can I verify that what I have is indeed Nafion?
EDIT: The issue has been resolved, read final post for resolution details.
Hi,
first I would try FTIR to identify the Nafion.
http://www.sciencedirect.com/science/article/pii/S0376738803006513
Kind regards
Peter
Thanks or the tip Peter! I will first talk to the sales technician from the distributor in case they made a error, but if they can't tell, I will certainly look at FTIR or other spectroscopic methods for confirmation.
Update: I casted Nafion from a Sigma-Aldrich Nafion solution and the film behaved the same way. It turns out my metal solutions were acid forms and the metals form complexes with the chlorides (or other ligands), which are anionic (for example, chloroplatinic acid consists of protons and [PtCl6]^-2 complexes). This still doesn't explain how BH4- makes it through the membrane though.
As of my knowledge ... membrane as such wont conduct protons...
Protons need some driving force to diffuse through the membrane ..
What was that driving force in your experiment .. ?
And also many other suppliers of nafion are there ... you can try one of them..
And i am also a customer of fuelcelletc ... I hope they never did mistake ...
Thanks for your response Partha. I was following a protocol outlined in an old paper (a seminal paper of the technique) and they used chloroplatinic acid, which in solution is an anionic PtCl6 complex. Nafion should allow ion-exchange with cations in solution as long as those ions are in excess relative to the sulfonate sites. Proton conductance is actually highly favorable in Nafion and will readily conduct without external driving forces beyond thermodynamics.
I read a handful of later papers that use a tetraamine platinumm complex , [Pt(NH3)4]^2+, which is a small charge cation that intuitively makes more sense. I am in the process of acquiring this salt in hopes of resolving my issue.
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