Atomic-level imaging of catalysts by scientists at the Department of Energy’s Oak Ridge National Laboratory could help manufacturers lower the cost and improve the performance of emission-free fuel cell technologies.
Fuel cells rely on costly platinum catalysts to enable the reactions that convert chemical energy into electricity. Alloying platinum with noble metals such as cobalt reduces the overall cost, but such alloyed catalysts vary in performance based on their atomic structure and processing history.
An ORNL team used scanning transmission electron microscopy to track atomic reconfigurations in individual platinum-cobalt nanoparticle catalysts as the particles were heated inside the microscope. The in-situ measurements—acquired in real time in the vacuum of the microscope column—allowed the researchers to collect atomic level data that could not be obtained with conventional microscopy techniques. The results are published in Nature Communications.
“This is the first time individual nanoparticles have been tracked this way—to image the structural and compositional changes at the atomic level from the start of an annealing process to the finish,” ORNL coauthor Karren More said.
Very small changes in the positions of platinum and cobalt atoms affect the catalyst’s overall activity and selectivity, so annealing—a gradual heating, holding, and cooling process—is often used to modify the alloy’s surface structure. The ORNL in situ microscopy experiments documented exactly what, when and how specific atomic configurations originate and evolve during the annealing process.
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