Invited: Bipolar Membrane Fuel Cells Using Anion Conductive Multiblock Copolymers

Anionic fuel cells are a possible route to overcoming fundamental issues with acid-based fuel cells. The issues include the high cost of platinum catalysts, complex water transport, and sluggish electrochemical reactions. In particular, a bipolar membrane composed of a cation conducting material and an anion conducting material has several additional advantages because each electrode can have an optimum pH, and water can be created at the cation/anion membrane interface close to where it is used at the air cathode.

Anion conductive multiblock copolymer membranes have shown promise for hydroxide conducting media. Anion conductive membranes have been synthesized with different block lengths and ion exchange capacities in order to maximize the ionic conductivity and understanding the relationship between chemical structures and water mobility in anion exchange membranes. The multiblock copolymers were synthesized by a polycondensation reaction between separately-prepared hydroxide-terminated oligomers and fluorine-terminated oligomers. The polymers were made ion conductive and hydroxide ion exchanged. The resulting anion conductive multiblock copolymers had higher conductivity than their random copolymer counterparts at the same IEC. The structure-property relationship of the ion conductive polymers, and bipolar membrane fuel cells constructed from them were characterized and will be reported.