Atomic-scale structure and composition of Pt3Co/C nanocrystallites during real PEMFC operation: A STEM–EELS study

Autor: Pascale Bayle-Guillemaud, Marian Chatenet, Laure Guétaz, Frédéric Maillard, Johan André, Miguel López-Haro, Elisabeth Rossinot, Nicolas Caqué, Laetitia Dubau
Rok vydání: 2014
Předmět:
Zdroj: Applied Catalysis B: Environmental. :300-308
ISSN: 0926-3373
DOI: 10.1016/j.apcatb.2014.01.034
Popis: The oxygen reduction reaction (ORR), which is the cathodic reaction in a proton-exchange membrane fuel cell (PEMFC) and in several other important processes, is a widely studied reaction. From the kinetics viewpoint, Pt is the best electrocatalyst and its activity can be increased upon alloying with a 3d-transition metal (Co, Ni, Fe, Cu). Aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy prove that the structural and compositional changes of Pt3Co/C nanoparticles during real-life PEMFC operation are much richer than previously thought from accelerated stress tests. Four different nanostructures are observed after 3422 h of operation in stationary mode: Pt, Pt–Co/C “hollow”, Pt–Co core–shell and Pt “bulk” nanoparticles. The presence of “hollow” nanoparticles in the aged catalytic layer is accounted for by the nanoscale Kirkendall effect, a vacancy-mediated diffusion mechanism in binary alloys where one species diffuses faster than the other. The oxygen reduction reaction specific activity of the “hollow” nanostructures is 1.5-fold that of the fresh Pt3Co/C cathode catalyst and 3-fold that of Pt/C nanoparticles, thereby offering a new route to synthesize highly active and durable PEMFC electrocatalysts.
Databáze: OpenAIRE
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