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.

https://www.homedepot.com/p/Daltile-Quarry-Tile-Red-Blaze-6-in-x-6-in-Ceramic-Floor-and-Wall-Tile-11-sq-ft-case-0Q40661P/202653720

36 dollars plus tax for 11 sq ft of  PEM / Cation Membrane material is a fantastically priced over the designer films

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4744959/

https://www.researchgate.net/publication/257205341_Comparing_the_short_and_long_term_stability_of_biodegradable_ceramic_and_cation_exchange_membranes_in_microbial_fuel_cells

http://www.clays.org/journal/archive/volume%2012/12-1-397.pdf

https://www.hindawi.com/journals/tswj/2015/864568/ good article related to my setup