Cost-efficient utilization of Pt in the oxygen reduction reaction (ORR) is of great importance for the potential industrial scale demand of proton-exchange membrane fuel cells. Designing a hollow structure of a Pt catalyst offers a great opportunity to enhance the electrocatalytic performance and maximize the use of precious Pt. Herein we report a routine to synthesize ultrathin icosahedral Pt-enriched nanocages. In detail, the Pt atoms were conformally deposited on the surface of Pd icosahedral seeds, followed by selective removal of the Pd core by a concentrated HNO3 solution. The icosahedral Pt-enriched nanocage that is a few atomic layers thick includes the merits of abundant twin defects, an ultrahigh surface/volume ratio, and an ORR-favored Pt{111} facet, all of which have been demonstrated to be promoting factors for ORR. With a 10 times higher specific activity and 7 times higher mass activity, this catalyst shows more extraordinary ORR activity than the commercial Pt/C. The ORR activity of icosahedral Pt-enriched nanocages outperforms the cubic and octahedral nanocages reported in the literature, demonstrating the superiority of the icosahedral nanocage structure.
Herein, we report an epitaxial-growth-mediated method to grow face-centered cubic (fcc) Ru, which is thermodynamically unfavorable in the bulk form, on the surface of Pd-Cu alloy. Induced by the galvanic replacement between Ru and Pd-Cu alloy, a shape transformation from a Pd-Cu@Ru core-shell to a yolk-shell structure was observed during the epitaxial growth. The successful coating of the unconventional crystallographic structure is critically dependent on the moderate lattice mismatch between the fcc Ru overlayer and PdCu3 alloy substrate. Further, both fcc and hexagonal close packed (hcp) Ru can be selectively grown through varying the lattice spacing of the Pd-Cu substrate. The presented findings provide a new synthetic pathway to control the crystallographic structure of metal nanomaterials.
Herein, we report an epitaxial-growth-mediated method to growf ace-centered cubic (fcc) Ru, which is thermodynamically unfavorable in the bulk form, on the surface of Pd-Cu alloy.I nduced by the galvanic replacement between Ru and Pd-Cu alloy, as hape transformation from aPd-Cu@Ru core-shell to ayolk-shell structure was observed during the epitaxial growth. The successful coating of the unconventional crystallographic structure is critically dependent on the moderate lattice mismatchb etween the fcc Ru overlayer and PdCu 3 alloy substrate.F urther,b oth fcc and hexagonal close packed (hcp) Ru can be selectively grown through varying the lattice spacing of the Pd-Cu substrate.The presented findings provideanew synthetic pathway to control the crystallographic structure of metal nanomaterials.
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