Phosphoric acid doped polybenzimidazole (PA – PBI) has been the most commonly used membrane for high temperature polymer electrolyte membrane fuel cell and hydrogen pump applications. Some of the limitations of PA – PBI arise from their weak acid – base interaction leading to PA loss under two scenarios: i.) temperatures above 180 °C that causes PA evaporation and ii.) low humidity operations were water supplants PA favorably within the acid-doped polymer host. PA doped polycation based membranes exhibit strong cation-anion electrostatic interactions that aid in PA retention up to 220 °C and curtail PA loss in the presence of water. However, several PA-polycations variants examined in our lab display lower proton conductivity when compared to PA – PBI because the PBI host features a higher PA loading due to its greater ion-exchange capacity. This talk will discuss a new class of high temperature, anhydrous proton conducting membrane based upon PA doped PBI – polycation blends. The polycation is quaternary benzyl pyridinium polysulfone. The blended membranes doped with PA displayed impressive proton conductivity up to 0.3 S cm<sup>-1</sup> with stability up to 240 °C and in the presence of humidified water. Similar proton conductivity results were attained for thin film ionomer variants implying that this material, unlike Nafion, does not lose its proton conductivity under thin film confinement in electrode layers. Furthermore, dielectric relexation microwave spectroscopy revealed that the polymer blends have a higher dielectric constant in comparison to the polycation alone and this partially accounts for the higher proton conductivity observed with the blended membranes. Finally, the talk will present fuel cell, electrolysis, and supercapacitor device performance in the temperature range of -70 °C to 220 °C demonstrating the versatility and effectiveness of these new polymeric materials for electrochemical energy conversion and storage.<br/>

High temperature proton exchange membranes based upon acid doped polycation: Polybenzimidazole blends for fuel cells, electrolysis, and supercapacitor devices

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.