Abstract
Conformal deposition of platinum as ultrathin shells on facet-controlled palladium
nanocrystals offers a great opportunity to enhance the catalytic performance while reducing
its loading. Here we report such a system based on palladium icosahedra. Owing to lateral
confinement imposed by twin boundaries and thus vertical relaxation only, the platinum
overlayers evolve into a corrugated structure under compressive strain. For the core-shell
nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass
activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively,
relative to a commercial catalyst. Density functional theory calculations indicate that the
enhancement can be attributed to the weakened binding of hydroxyl to the compressed
platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the
core-shell nanocrystals is still four times higher than the commercial catalyst. These results
demonstrate an effective approach to the development of electrocatalysts with greatly
enhanced activity and durability.
