High-Density Pd Nanorod Arrays on Au Nanocrystals for High-Performance Ethanol Electrooxidation.

In the synthesis of Au/Pd bimetallic nanocrystals, a layer-by-layer growth is favored, owing to the low bonding energy between Pd atoms ( EPd-Pd) in comparison with EAu-Pd, resulting in homogeneous core/shell nanostructures. Herein, we demonstrate designed synthetic tactics to unconventional Au/Pd heterostructures through a deposition-dominant growth pathway of the newly reduced Pd atoms, which break the intrinsically favored layer-by-layer growth. Pd thus grows on Au seeds in a heterogeneous nucleation manner. The resulting anisotropic Pd nanorods array on the two basal facets and three side facets of the Au triangular seeds in a high density to form 2D/1D Au/Pd heterostructures. It is noticed that Pd nanorods align in an extremely high order. They grow almost in a row with the base of the rod located overlapped on the Au surface. This versatile approach has been also applied to other Au nanocrystal seeds, involving hexagonal nanoplates, circular nanodisks, nanorods, and nanobipyramids. Furthermore, the 2D/1D Au/Pd heterostructures exhibit an enhanced electrocatalytic performance toward ethanol oxidation in alkaline condition, owing to their unique structure and the exposure of Au. We believe that our synthetic strategy is highly valuable for the construction of multimetallic nanostructures with desired architectures and thus intriguing properties.