So I have been doing a bit of reading on various materials. There have been studies conducted on earthenware membranes. This was a clever suggestion from Mechanicus. Terra Cotta is one of these. Though I could spend lots of money on custom made film membranes, in the spirit of hackaday I need to HACK something that is both common , repeatable and effective. I believe earth based/ clay membranes would be much better as the cost is less than 10 percent that of a designer membrane from somewhere like fuelcellstore.com for example.
36 dollars plus tax for 11 sq ft of PEM / Cation Membrane material is a fantastically priced over the designer films
https://www.hindawi.com/journals/tswj/2015/864568/ good article related to my setup