In-Situ Electrochemical Microscopy of PEM Fuel Cell Materials

High-resolution imaging of the structural changes to Pt-based catalyst nanoparticles supported on carbon blacks using in-situ electrochemical liquid cell transmission electron microscopy (TEM) are being correlated with the behavior of similar materials incorporated in membrane electrode assemblies (MEAs) subjected to accelerated stress tests (ASTs), to elucidate catalyst and catalyst-support degradation phenomena contributing to fuel cell performance loss. Specialized in-situ holders for the TEM have been developed that incorporate patterned electrodes within a closed liquid flow cell that enable the interactions between catalyst particles and their supports to be imaged during potential cycling in relevant liquid electrolytes, such that the critical stages of materials corrosion during fuel cell operation can be imaged in real time at nm-scale resolution. The direct TEM observations of the changes to the catalyst (Pt dissolution and particle growth/coalescence) and carbon supports (mechanisms of progressive support corrosion) during in-situ electrochemistry, combined with the post-mortem evaluation of cathode layers comprised of similar Pt/C materials after AST of MEAs, provide an unprecedented means by which to “capture” catalyst and catalyst-support degradation mechanisms such that materials optimization strategies can be implemented to enhance fuel cell durability.

Research sponsored by (1) the Office of Fuel Cells Technologies, Office of Energy Efficiency and Renewable Energy, the U.S. Department of Energy and (2) ORNL’s Center for Nanophase Materials Sciences, Scientific User Facilities Division, Office of Basic Energy Sciences, the U.S. Department of Energy.