Preparation and Characterization of Highly Stable Ionomers and Ionomer Membranes for Medium Temperature Fuel Cells

• Applicant: Professor Dr. Emil Roduner
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2004 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5417402

• Final Report Year: 2008

Final Report Abstract

The most successful part of the project was the investigation of the reaction of monomers with HO" radicals. It was found that the degradation chemistry depends strongly on pH and that it is particularly severe in a window between pH 9 and 14. Even though the general condition in a fuel cell is acidic, basic conditions can occur locally when a large current is drawn from the cell and the proton concentration may decrease in areas of fuel starvation or at near efficient catalyst grains at the cathode which reside in regimes where proton transport through the membrane is not sufficiently efficient. Two major limitations of the project were encountered: Some of the monomers may themselves be subject to photolysis so that the detected radicals may not be the product of HO" reactions. This can be checked in experiments in the absence of hydrogen peroxide. Secondly, some of the monomers are not sufficiently soluble in aqueous solutions. Attempts to increase solubility by addition of other solvents like methanol failed, not because solubility was not increased but because the hydroxyl radicals would under these conditions react preferentially with the much more abundant methanol. The same limitation holds for experiments with polymers in solution.

Publications

• Comparative DFT study of non-fluorinated and perfluorinated alkyl and alkyl-peroxy radicals. Chem. Phys. Lett. 402 (2005) 485-490
  S. Mitov, A. Panchenko, and E. Roduner
  
• Degradation of Polymer Membranes Used in Fuel Cell Applications. In: S. Schlick, editor, Advanced ESR Methods in Polymer Research. John Wiley & Sons, New York, 2006. ISBN: 0-471-73189-7
  E. Roduner and S. Schlick
  
• Oxidative and Photochemical Stability of lonomers for Fuel Cell Membranes. Helv. Chim. Acta, 89 (2006) 2354-2370
  S. Mitov, O. Delmer, J. Kerres, E, Roduner
  
• Preparation and characterization of highly stable ionomers and ionomer membranes for medium temperature fuel cells. Fuel Ceils, 6 (2006) 413-424
  S. Mitov, B. Vogel, E. Roduner, H. Zhang, X. Zhu, V. Gogel, L. Jörissen, M. Hein, D. Xing, F. Schönberger, J. Kerres