Electron Microscopy Study of Platinum Group Metal-Free Catalysts Synthesized By High-Throughput Approaches

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Platinum group metal-free (PGM-free) catalysts are being explored for the oxygen reduction reaction in proton exchange membrane fuel cells. Since both their mass activity and durability are lagging their more developed Pt-based counterparts, accelerated catalyst discovery is this area is sorely needed. High-throughput approaches to catalyst synthesis and testing are an ideal approach to exploring this broad design space which includes precursor type, transition metal loading, and pyrolysis temperature. A range of such materials were synthesized and tested in Argonne National Laboratory’s High Throughput Research Laboratory and characterized by a variety of advanced analytical techniques, including scanning transmission electron microscopy (STEM). Low-voltage, aberration-corrected STEM was coupled with spectroscopic techniques to quantify atomic scale differences in the morphology of each catalyst. These highly localized measurements were coupled with X-ray techniques, including X-ray photoelectron spectroscopy and X-ray absorption spectroscopy, to achieve a more complete view of the structural properties which impact mass activity and durability and the synthesis conditions which achieve such structures. These results, along with the application of new STEM imaging modalities and combinatorial techniques to accelerate throughput, will be presented. This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office under the Electrocatalysis Consortium (ElectroCat). Microscopy performed as part of a user project at ORNL’s Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility.