High Temperature, Low Relative Humidity, Polymer-type Membranes Based on Disulfonated Poly(arylene ether) Block and Random Copolymers Optionally Incorporating Protonic Conducting Layered Water Insoluble Zirconium Fillers

摘要

Proton exchange membrane fuel cells (PEMFC) are well recognized to be environmentally attractive alternative automotive, stationary and portable power sources for the future. Arguably, the most important criterion for PEMFC is the need to maintain proton conduction over a range of temperatures, under partially hydrated conditions. State of the art PEMFC systems are based on perfluorosulfonic acid ionomer membranes such as Nafion. Our research group has been engaged with the DOE to better understand how molecular structure of the polymeric membrane influences protonic conductivity as well as other important issues which currently limit the development of PEMFC for commercial applications. Our laboratory has emphasized the synthesis and characterization of wholly aromatic 4,4'-biphenol based partially disulfonated poly(arylene ether sulfone) random copolymers as potential PEMs. These copolymers have been defined by a shortened name, BPSH-xx where BP stands for biphenol, S is for sulfonated, and H denotes the proton form of the acid where xx represents the degree of disulfonation. In addition hydroquinone(HQSH) based disulfonated poly(arylene ether sulfone) random copolymers were also prepared and studied. HQSH has the potential for being the more economical of the two. Both series of copolymers with varying degree of disulfonation were characterized and under fully hydrated conditions, they were comparable and even better than the commercially available Nafion. Open circuit (OCV) voltage measurements done under DOE support at UTC showed that their stability at 100C and 25% RH, in pure H2/O2 was actually better than Nafion, regardless of the apparent drawbacks as shown by Fenton tests. However, proton transport was limited at low hydration level for the random copolymer and was less attractive than Nafion.