Atomic Structure and Composition of "Pt3Co" Nanocatalysts in Fuel Cells: An Aberration-Corrected STEM HAADF Study

Abstract

Pt3Co nanoparticles are used to promote the oxygen reduction kinetics and increase the efficiency of proton exchange membrane (PEM) fuel cells. For the first time, aberration-corrected scanning transmission electron microscopy (STEM), STEM image simulations, and DFT calculations are combined to provide insight into the origin of enhanced catalysis of Pt3Co nanoparticles. Acid-leached nanoparticles exhibit a solid-solution structure but heterogeneous composition, while heat-treated nanoparticles exhibit an ordered structure, except for the first three surface layers where Pt enrichment is observed.