Morphology and lateral strain control of Pt nanoparticles via core-shell construction using alloy AgPd core toward oxygen reduction reaction.

Controlling the morphology of Pt-based nanomaterials can be an effective way to improve the catalytic activity on a mass basis. Herein we demonstrate for the first time the synthesis of monodispersed core-shell AgPd@Pt nanoparticles with multiply twinned structures. These multiply twinned particles (MTPs), which possess the icosahedra structure, exhibit superior catalytic activity toward oxygen reduction reaction (ORR) in fuel cells. The Ag component of the alloy AgPd inner core is crucial for the construction of the multiply twinned structure of the core-shell nanoparticles, while the Pd component is used to reduce the tensile strain effect of the Ag on the deposited Pt layers, rendering the Pt binding energy in core-shell AgPd@Pt MTPs to be close to that of commercial Pt nanoparticles. The enhanced ORR activity of AgPd@Pt/C can be explained in terms of a much higher surface fraction of atoms on the (111) facets for icosahedral MTPs. This core-shell structure offers an interesting example to investigate the morphology and lateral strain effect of the substrate on the deposited layers, and their influence on the catalytic activity of metal catalysts.