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Colloidal structure of ionomer solutions

Advances in Electrocatalysis, Materials, Diagnostics and Durability

Conductive membranes for low-temperature fuel cells

Characterization

  1. G. Gebel

Published Online: 15 DEC 2010

DOI: 10.1002/9780470974001.f500024

Handbook of Fuel Cells

Handbook of Fuel Cells

How to Cite

Gebel, G. 2010. Colloidal structure of ionomer solutions. Handbook of Fuel Cells. .

Author Information

  1. Laboratoire SPrAM, INAC, CEA, Grenoble, France

Publication History

  1. Published Online: 15 DEC 2010

Abstract

The discovery of an efficient process to “dissolve” Nafion at the beginning of the 1980s has boosted the development of efficient fuel cells. Indeed, the preparation of electrodes with very high active areas, of homogeneous and thin membranes by solution casting, and of new composite membranes then became possible. After a short review on swelling properties and dissolution of Nafion membranes, this article focuses on the structure and properties of these solutions and on the obtaining of membranes by solution casting. The small-angle X-ray and neutron scattering studies combined with light scattering and magnetic resonance data point out the colloidal structure of these solutions. The question of the existence of isolated polymer chains is still under debate. However, the analysis of the dilute solution scattering patterns revealed the presence of large elongated particles with a size directly related to the volume of the fluorinated polymer associated to each ionic group. This structure was confirmed by electron and atomic force microscopy pictures. The particle diameter was shown to be strongly related to polymer solvent interactions. This parameter also has a great influence on the properties of the solution-cast films and consequently it has a great impact on the electrode microstructure in membrane electrode assemblies (MEA). The light scattering studies revealed a limited stability with a strong predisposition to aggregate in larger particles. A post-thermal treatment is often necessary to restore properties similar to those of the pristine Nafion membrane.

Keywords:

  • ionomer dispersion;
  • Nafion solution;
  • perfluorsulfonated membranes;
  • structure;
  • solution-cast membranes