In Situ and Ex Situ Experiments on Sulfonated PARMAX

Lancucki, Lukasz, Krzysztof Kruczala, Marek Danilczuk, and Shulamith Schlick

Fuel cells (FCs) are electrochemical devices that convert the chemical energy directly into electricity and have potential to become alternative sources of clean energy for transportation, portable and stationary applications. Proton exchange membranes (PEMs) FC are the most studied out of the wide range of types. In these FCs the ionomer membranes perform an essential role by separating the anode and cathode sections, thus allowing proton conductivity. Nafion® is the classic perfluorinated membrane commonly used as a proton conducting polymer, but its price is prohibitive. For this reason, great efforts are made to obtain proton conducting protonated membranes that are durable at 85oC.1 Here we present experimental results, for sulfonated poly(benzoyl paraphenylene) – SParmaxÒ 1200.2

 

ParmaxÒ1200 is a commercially available high performance amorphous thermoplastic, with excellent chemical and physical properties, including great thermal-oxidative stability. After sulfonation, this polymer has the proton conductivity necessary for FC applications. Membrane electrode assemblies (MEAs) were investigated in a FC inserted in the resonator of the ESR spectrometer.3 Direct ESR and spin trapping methods were applied to study the system. The in situ spin trapping experiments show presence of HO•, HOO•, H•, D• in the operating FC.4 H• and D• radicals were detected at the anode side, and after longer time of operation also at the cathode side. In contrast to the in situ results for MEAs based on Nafion,3 no adduct of carbon centered radicals (CCRs) were detected for SParmax.5

Complementary investigation was done by FTIR-ATR, differential scanning calorimetry (DSC) and thermogravimetry coupled with quadrupole mass spectrometry (TG-QMS). The thermogravimetric analysis confirms the excellent thermal stability of this polymer, revealing the loss of sulfonic groups above 150 oC.

 

Acknowledgements: This research was supported by the U.S. Department of Energy Cooperative Agreement no. DE-FG36-07GO17006, NSF (Polymers Program), and General Motors.

 

[1] Hickner, M. A.; Ghassemi, H.; Kim, Y. S.; Einsla, B. R.; McGrath J. E. Chem. Rev. 2004, 104, 4587−4612.

[2] Ha, Y. H.; Scott, C. E.; Thomas, E. L. Polym. 2001, 42, 6463-6472.

[3] Danilczuk, M.; Coms, F.D.; Schlick, S. J. Phys. Chem. B 2009, 113, 8031–8042.

[4] Danilczuk, M.; Coms, F.D.; Schlick, S. Fuel Cells 2008, 8, 436-452.

[5] Manuscript in preparation.