Shape‐controlled Pt‐based seeds lead to completely different M/Pt (M = Ru or Rh) structures of nanobox or octapod. Unusually high catalytic activities of Pt@Ru octapod toward the oxygen evolution reaction are observed due to a core–shell effect.

Simultaneously growing multiple nanocrystallites in a crowded space can cause a shortage of precursors, and this can lead to a vertical growth of nanocrystallites on a given substrate. The presence of surfactant-surfactant interactions among adjacent nanocrystals can also place a unique structural constraint on the growing nanocrystallites, resulting in novel nanocrystal facet control. Herein, we report the growth of Rh on Au@Pt nanowires with multiple twinning boundaries, which are found along the entire nanowire length. The Au@Pt nanowires exhibit numerous bead-like structures, resulting from the preferred Pt deposition on the twinning boundaries, which can serve as nucleation sites for Rh. The heteroepitaxial growth of Rh on the Au@Pt nanowires results in unusual crystal growth behaviours. First, novel morphologies of Rh nanorods, nanoplates, and tangled manes are obtained temperature-dependently, which are not obtained in the absence of the Au@Pt nanowire substrate. Secondly, the thickness of vertically grown nanorods and nanoplates is tightly controlled. We also report the structure-catalytic activity relationship on the catalytic hydrogenation of phthalimides by the new Rh nanostructures.

Regioselective growth of a heterophase on facet-controlled nanocrystals is an indispensable step towards generation of geometrically well-defined heteronanoarchitectures. The growth of a heterophase usually occurs on the most unstable surface features of a nanoparticle, such as vertices and edges, and therefore the ability to control the surface energy of facet-controlled nanocrystals is crucial for the rational synthesis of nanoarchitectures. It is, however, not easy to attain the ability to regioselectively grow a heterophase on a facet-controlled nanocrystal. Herein we introduce a simple strategy to pinpoint the site of heterophase growth on the surface of a faceted nanocrystal by controlling the concentration of surface-stabilizing moieties. Specifically, we show the regioselective growth of Au on a PtZn concave nanocube, covered with surface-bound CO moieties, forming two completely different Au–PtZn heteronanostructures of a filled-concave Au–PtZn surface mosaic nanocube and a vertex-covered Au–PtZn octapod. We also show their application in surface-enhanced Raman scattering (SERS)-based detection of small molecules.

Facet‐controlled nanoparticles as a substrate for heteroepitaxial growth can lead to disparate growth kinetics on different structural sites. H. Yang, K. Lee, and co‐workers report the synthesis of two completely different Pt@M heteronanostructures (M = Ru or Rh), namely, Pt@M nanoboxes and Pt@M octapods, using Pt cube seeds with slightly different morphologies. On page 4462, they identify the nanostructural features which boost catalytic performance toward the oxygen evolution reaction.