Immobilization of heteropolyacids in PEM fuel cell membranes via copolymerization

Abstract

Nafion is the current standard by which PEM fuel cell membranes are measured. It is a PFSA (perfluoro sulfonic acid) polymer that is used to conduct ions such as protons. This material is only useful at low temperature (less than 100 degrees celsius) and high relative humidity due to protons being transported by water which is not practical for a fuel cell. Research is currently being done to create a new membrane that does not contain PFSA, instead membranes are made using heteropolyacids (HPAs). HPAs are useful because they are strong inorganic acids that have a high water of hydration, meaning a humidifier may not be necessary in a fuel cell. Another positive aspect of HPAs is the ability of protons to hop from HPA molecule to HPA molecule. One limitation of HPAs is their solubility in water. This research is focused on immobilizing the HPA by functionalizing it with an easily polymerizable group so that it becomes a monomer that can be used to make copolymers. Two HPA systems are being presented here, HPA-ethylene and HPA-butyl acyrlate. It is possible that these systems will be more effective than PFSA membranes.