(Invited) Crosslinked High Temperature Polymer Electrolyte Membranes

Abstract

High temperature polymer electrolyte membranes containing basic units that are able to interact with strong protic acids providing ionically conductive composite membrane have shown respectable performance and long operational stability. Further increase of the operation temperature and even an increase on the obtained conductivity values would facilitate the construction of efficient systems providing both electricity and heat, increasing thus the total efficiency. Initial attempts to stabilize the HTPEM electrolyte membranes through covalent crosslinking have proven that the operation temperature can be shifted up to 220oC 1,2. Different crosslinking methodologies have been tested to stabilize either PBI or aromatic polyethers bearing pyridine units3,4. In the present work we focused on the optimization of the crosslinking methodology using side double bonds and we also develop new crosslinking methodologies leading to wholly aromatic crosslinked structures. Different type of crosslinkers have been used, controlling thus the acid doping ability of the final membranes while the use of dopable crosslinkers that enable the high acid uptake and retention. Moreover, depending on the chemical structure of the crosslinked membranes, a significant increase of the conductivity values of the final acid doped composite membranes was obtained. High temperature operation as the one achieved here enables the use of liquid feed like methanol in a compact methanol reformer-high temperature PEM fuel Cell setup that is under construction and testing5.