(238a) Tuning Transport and Reaction across Length Scales for Next Generation Electrochemical Devices

Electrochemical systems such as fuel cells, electrolyzers, and reversible fuel cells require complex multiphase transport and reaction at poorly defined interfaces. This talk will describe new approaches to design both catalysts and electrodes for faster transport and reaction. We have recently demonstrated that the use of intermetallic nanoparticle catalysts such as L1₀-PtCo can enable significant improvements in long-term performance due to improved stabilization of base metal in the ordered lattice, while use of carbon supports with controlled pore size distribution provides further advantages by protecting metal nanoparticles from degradation or poisoning by ionomer. Recent results and future directions for this catalyst research will be discussed. While kinetic performance and durability of these catalysts is promising, performance at high power densities continues to be limited by slow O₂ transport. Several factors, including slow diffusion through ionomer films, Knudsen diffusion through micropores, and pore blockage by liquid H₂O contribute to these transport limitations. Design of unconventional electrode structures that can minimize these limitations is needed to enable full utilization of cathode catalysts. New hierarchical electrode structures capable of reducing these transport losses will be presented.