Is PVA membrane stable in alkaline (KOH) medium? What is the maximum alkaline stability efficiency of PVA membrane for alkaline fuel cell application?
Dear Dr. S. Rajesh Kumar,
Generally, PVA membranes are very stable in KOH solutions. For example, it is accepted that the ionic conductivity of those membranes is measured at 25 oC and when doped with 6 M KOH solution.
http://www.electrochemsci.org/papers/vol8/80100949.pdf
https://www.google.ps/search?biw=1366&bih=667&q=related:www.springer.com/cda/content/document/cda_downloaddocument/9781461457848-c1.pdf%3FSGWID%3D0-0-45-1367006-p174671202+pva+membrane+for+alkaline+fuel+cell+applications&tbo=1&sa=X&ved=0ahUKEwi_vOLm3ZjMAhVkJpoKHVtUCN0QHwgsMAE
http://www.sciencedirect.com/science/article/pii/S0013468613014667
Hoping this will be helpful,
Rafik
Dear Prof. Rafik Karaman,
Thank you very much for kind reply and answers. The research articles and google link is very much helpful to know about alkaline stability of PVA membrane. Thank you sir...
Regards
Rajesh
I would add only a minor note. PVOH is obtained from PVAc by hydrolysis, which is never complete. Soaking in alkaline medium may hydrolize the the rest of the ester groups so a minor modification of the properties may happen.
I have studied by FTIR PVA obtained for preparation of super-high-oriented, super-strong mono-filaments (see the publications of prof. Tetsuo Kanamoto from Tokyo Science University). The final - after hydrolysis content of acetate groups was less than 0.01-0.02%. I am sure that such a miniscule concentration of residual acetate groups - hardly can affect the PVA properties.
Dear Prof. Leonid V Vladimirov,
Thank you very much for kind reply and answers.
Regards
Rajesh
Dear Prof. Gyorgy Banhegyi,
Thank you very much for kind reply and answers.
Regards
Rajesh
The answer to this really depends on what you're trying to do with your alkaline fuel cells (hydrogen fuel cells? DMFCs?). Even if PVA is stable when doped and fully hydrated at room temperature, it needs to be stable when it's somewhat dried out and heated. Altogether, you can't make a stable, high-performance alkaline exchange-membrane fuel cell with this system. The results weren't terrible, but there's a reason no stability data was reported even when the membrane was crosslinked and the cell run at room temperature, and the catalyst layers were terribly resistive, likely due to the absence (or instability) of ionomer. http://www.electrochemsci.org/papers/vol8/80100949.pdf
FuMA-Tech FAA-3 isn't fantastic, but as Tokuyama has stopped selling their membranes to researchers, it's currently the best buyable material for making AEMFCs. No official structure has been given, but best guess is that it's something along the lines of poly(arylene sulfone)-type with DABCO-type quaternary ammonium groups. I've shown it's also usable as a high-performance ionomer with some process control to rid the CLs of high-boiling solvent. http://jes.ecsdl.org/content/163/5/F353.full
This is the best review in the AEMFC field to date, and should help give you an idea where the field is looking for answers to the question of stability. http://pubs.rsc.org/en/content/articlepdf/2014/ee/c4ee01303d
There's also a DoE report coming out by July based on the 2016 meeting in Phoenix, so that's something to watch for current targets / ideas in the field.
Dear Benjamin,
Thank you very much for your kind reply and answer to my question. Your answer and references are very much useful to me.
Hi Dr. S. Rajesh Kumar ,
As Gyorgy Banhegyi said, KOH will cause excessive hydrolysis of Acetate groups in PVA membrane. It will beneficially insolubilise the membrane, favors cross-linking, improve its mechanical integrity for respective application.
But, can anyone explain, how does is affect the ionic conductivity of membrane?