Cation Exchange Membranes are proton-conductive polymer film, also known as electrolyte or ionomer, that allow only protons to cross-over (cation exchange), the key function of proton exchange membrane fuel cells and water electrolyzers.

Basically, cation exchange membranes perform as a separator and solid electrolyte in a variety of electrochemical cells that require the membrane to selectively transport cations across the cell junction.  The polymer is chemically resistant and durable.