Dodecahedral Au@Pd nanocrystals with high-index facets and excellent electrocatalytic activity and highly efficient surface-enhanced Raman scattering enhancement.

We synthesize the three-fold symmetric shield-like Au@Pd core-shell nanocrystals, enclosed predominantly by high-index {541} facets with kinks, through the simultaneous reduction of Au and Pd ions in the presence of triangular Au nanocrystal seeds in aqueous solution at room-temperature. The obtained shield-like Au@Pd core-shell nanocrystals exhibit superior electrocatalytic activity for the oxidation of ethanol and unique near-field enhancement property with a highly sensitive surface-enhanced Raman scattering (SERS) response. These excellent properties can be ascribed to the presence of sharp corners and edges as well as high-index faceted Pd-rich shell in the shield-like Au@Pd core-shell structure. We also investigate the mechanism for the formation of three-fold symmetric shield-like Au@Pd core-shell nanocrystals.