a sheet having anion exchange functionality and a sheet having cation exchange functionality are juxtaposed and joined by current bonding into a unitary bipolar membrane . this may be done without added reactants or bonding agents by placing the two - layer assembly between opposed electrodes in a fluid cell , preferably at pressure , and applying power across the cell to split water in a junction region of the membrane assembly . preferably the anion exchange sheet is treated with an iron salt solution so as to incorporate or immobilize the metal in the polymer during the current bonding process , and enhance operating characteristics of the bipolar junction . membrane peel strength is comparable to or greater than that of an underlying sheet of ion exchange material , but the bonding is fully reversible , e . g ., by soaking in a concentrated solution . preferably both sheets include an aromatic backbone or cross - linker component . one membrane may be a self supporting membrane , such as a conventional electrodialysis exchange membrane of 5 - 50 mil thickness , while the other may also be a commercial membrane of opposite exchange type and of similar strength or thickness , or may be specially manufactured to tailor its performance in the completed membrane . for example , one or both starting sheets may be manufactured with a pore former or may otherwise have its porosity , cross - linking , strength , ion rejection characteristics or thickness tailored for more effective bipolar operation — for example , to enhance transport or diffusion , resist shear or mechanical forces , improve chemical resistance to splitting products or species in the intended feed , or the like . preferably , prior to contacting and bonding , the anion exchange membrane is treated with a group viii metal salt . the current - bonded unitary bilayer construction remains contact bonded over its surface and resists degradation in normal use .