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Platinum was coated on the surfaces of copper nanocubes to form Cu–CuPt core–alloy–frame nanocrystals with a rhombic dodecahedral (RD) shape. Co-reduction of Pt2+ ions and residual Cu+ ions in the supernatant of the Cu nanocube solution followed by the interdiffusion of Cu and Pt atoms over the core–shell interface allowed their formation. Growth in the ⟨100⟩ directions of the {100}-terminated Cu nanocubes resulted in the {110}-faceted rhombic dodecahedra. By the introduction of additional Pt precursor, the {100} vertices of the Cu–CuPt RD nanocrystals could be selectively extended to form spiny CuPt RD nanocrystals. After removing the Cu core template, both CuPt alloy RD and spiny CuPt alloy RD nanoframes (NFs) were obtained with Pt/Cu ratios of 26/74 and 41/59, respectively. Abundant surface defects render them highly active catalysts due to the open frame structure of both sets of NFs. The spiny RD NFs showed superior specific activity toward the oxygen reduction reaction, 1.3 and 3 times to those of t...

Rhombic dodecahedral and highly edge- and corner-truncated octahedral gold nanocrystal cores with entirely or significant {110} faces were employed to investigate the core–shell orientation relationship of Au–Cu2O core–shell heterostructures. By increasing the volume of reductant added, we synthesized Au–Cu2O face-raised cubes, cuboctahedra, and octahedra. TEM characterization indicates a fixed core–shell orientation relationship. The {100}, {110}, and {111} facets of the gold cores align parallel to the corresponding faces of the Cu2O shells. Structural requirements of the gold cores for the preparation of Au–Cu2O stellated icosahedra indicate that icosahedral gold nanocrystals are good candidates. Use of trisoctahedral nanocrystal cores cannot generate stellated icosahedra, but unusual face-raised octahedra with V-shaped {111} edges can be synthesized. Core–shell cubes, face-raised cubes, core–shell octahedra, and face-raised octahedra were examined for their comparative photocatalytic activity toward t...