Fuel Cells Using the Protic Ionic Liquid and Rotator Phase Solid Electrolyte Principles

The concept of ionic liquids, formed by proton transfer from Bronsted acid to Bronsted base, serving as the proton transport media in fuel cells is evaluated at several levels. Firstly a wide range of protic ionic liquids formed from acids of a wide range of acid strengths to a variety of nitrogenic bases of different base strengths, nearly 100 in all, has been synthesized and characterized. A proton free energy level diagram, based on aqueous solution pKa data, has been developed to permit predictions of the properties of arbitrarily chosen acid-base pairs, and a modified glass electrode to directly study the proton transfer energetics, has been developed. Secondly, a class of siloxane polymers with pendant amine, or alternatively, pendant sulfonic acid groups, has been synthesized, and polymeric salts formed by neutralizing the pendant groups with acids or bases respectively have been formed and characterized. Their ability to imbibe the ionic liquids without loss of mechanical strength has been tested and conductivities up to 10mScm, at 100 degrees C, has been evaluated. Finally, the assembly of gas diffusion fuel cells running at up to 150 degrees C, using either the PILs or the PIL-swollen membrane as the electrolyte, has been undertaken.