Branched nanocrystals display interesting optical and catalytic properties on account of their high surface areas and tips with small radii of curvatures. However, many synthetic routes toward branched nanocrystals result in inhomogeneous samples on account of asymmetric branching. Seed-mediated coreduction is a recently developed route to symmetrically branched nanocrystals where the symmetry of the seeds is transferred to the final stellated morphologies. Here, general guidelines to stellated nanocrystals are outlined by surveying coreduction of Au and Pd precursors in the presence of a variety of shape-controlled Au seeds to achieve Au/Pd nanostructures. Single-crystalline, twinned, and anisotropic seeds were analyzed to expand the classes of stellated nanostructures synthetically accessible. Significantly, single-crystalline Au seeds adopt {100}-terminated intermediates prior to branching, regardless of initial seed shape. We compared these results with those obtained with shape-controlled Pd seeds, and seed composition was identified as an important synthetic parameter, with Pd seeds being more resistant to shape changes during overgrowth. This difference is attributed to the greater diffusion rate of Au atoms on Au seeds compared to Au atoms on Pd seeds. These results provide guidelines for the seeded synthesis of symmetrically branched nanocrystals and architecturally defined bimetallic nanostructures in general.

This paper describes the development of a facile and environmentally friendly strategy for supporting palladium nanoparticles (Pd NPs) on multiwalled carbon nanotubes (MWCNTs) with ethanol as the solvent/reducing agent, potassium tetrachloropalladate(II) (K2PdCl4) as the Pd precursor, and polyvinylpyrrolidone (PVP) as the surface modifier. More specifically, our approach was based on the nonbonding interaction between MWCNTs and PVP, which is a cheap, nontoxic, and commercial polymer. As PVP can serve not only as a surface modifier but also as a stabilizing agent for Pd NPs, the utilization of additional functionalization steps, reducing agents, and stabilizers was not required to achieve uniform Pd deposition over the MWCNTs. Our results demonstrate that Pd NPs below 5 nm in diameter can be directly supported on MWCNTs by this route. Also, sequential Pd‐reduction steps can be employed to improve the coverage of Pd NPs at the MWCNT surfaces, although this can also lead to the formation of larger Pd particles or aggregates. The electrocatalytic activity for ethanol oxidation was investigated as a function of the composition and structure of the materials produced, in which MWCNTs decorated with Pd NPs of smaller sizes and lower coverages displayed the highest activities. The results described herein suggest that our approach may serve as a simple platform for the synthesis of MWCNTs decorated with metal NPs with well‐defined morphologies and uniform dispersion for electrochemical and catalytic applications.

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Invited for the cover of this issue is the group of Pedro