(642d) Tailoring Low Humidity and High Temperature Proton Conduction Using Cerium Oxide Based Nanocomposite Membranes

Elevated temperature operation (120 ^oC -200 ^oC) has been of growing interest for proton-exchange membrane fuel cells (PEMFCs) due to wide-ranging advantages – from improved fuel cell efficiency, increased tolerance to fuel impurities and allowing a simplified thermal and humidity management. However, operation conditions of today’s PEMFCs are limited to high humidity and low temperatures (< 100 °C) due to the polymer electrolyte. Elevated temperature operation of PEMFCs is precedent upon the performance and integrity of the proton exchange membrane. This work explores a nanocomposite approach towards membrane design by incorporation of Cerium oxide nanoparticles in a polymer matrix leveraging the observation of elevated temperature, low humidity proton conductivity in thin films of cerium oxide (CeO₂) nanocrystals. This anomalous conductivity is due to reactivity of adsorbed water at the CeO₂ surface. Synthesized CeO₂ nanocrystals (size ~ 4nm) are embedded in polymer matrix materials based on poly vinyl imidazole or poly ethylene oxide to enhance proton mobility. These membranes are characterized for their proton conductivity measured under low humidity and intermediate temperature conditions and compared against commercially available perfluoro sulfonic acid membranes.