Lattice Strain Distributions in Individual Dealloyed Pt-Fe Catalyst Nanoparticles.

Lattice strain is considered to play an important role in the oxygen reduction catalysis on Pt-based catalysts. However, so far, direct evidence of the lattice strain in the catalyst nanoparticles has not been achieved. By using aberration-corrected high-resolution transmission electron microscopy combined with image simulations, a unique core-shell structure, that is, a percolated lattice-contracted Pt-Fe alloy core and a Pt-rich surface with a gradient compressive strain, was directly demonstrated within individual dealloyed Pt-Fe nanoparticles and thus provides direct evidence for the strain effect on their enhanced oxygen reduction activity.