Polymer electrolyte fuel cells (PEFCs) hold great promise as a sustainable energy technology, and there is significant cost motivation to develop new electrode designs with low platinum (Pt) loading. However, recent reports on conventional, carbon-supported, reduced Pt-loading PEFC electrodes have shown significant performance losses due to oxygen transport resistance through a thin-film ionomer at high current-densities. These findings have motivated a search for alternative electrode designs that do not rely on ionomers for proton conduction. Nano-structured thin-film electrodes and several other extended-surface area electrodes have demonstrated promising power densities and durability, however underlying ion transport mechanisms and associated reaction kinetic pathways are still ill understood. The proposed project aims to determine the specific factors which limit performance of PEFCs using thin-film electrodes and allow for work to progress on overcoming these hurdles. The PI plans to integrate research findings into teaching and develop a broad range of educational and outreach activities to a diverse range of K-12 students, including underrepresented minorities, to foster excitement about renewable-energy and STEM careers.
The proposed research has three main objectives: (1) Elucidate the fundamental mechanisms of ion transport in water-filled Pt and dispersed, carbon-supported Pt electrodes. (2) Establish the operational window (current, temperature and relative humidity) for ion-conduction mechanisms under oxygen reduction reaction (ORR) currents. (3) Determine the participating ions and mechanisms that occur in ORR in water-filled electrodes and create tailored electrode designs to enhance the rate of ORR. The separation of competing ion transport mechanisms will be accomplished through ex-situ four-point probe experiments combined with in-operando electrochemical techniques and modeling studies. The proposed work has the potential to advance the current understanding of the mechanisms of ion transport in ionomer-free PEFC electrodes.
