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

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.