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We have developed a synthesis method of rhombic dodecahedral Pd@Pt core-shell nanocrystals bound exclusively by {110} facets with controlled numbers of Pt atomic layers to study the surface strain-catalytic activity relationship of Pt{110} facets. Through control over growth kinetics, the epitaxial and conformal overgrowth of Pt shells on the {110} facets of rhombic dodecahedral Pd nanocrystals could be achieved. Notably, the electrocatalytic activity of the Pd@Pt nanocrystals toward oxygen reduction reaction decreased as their Pt shells became thinner and thus more in-plane compressive surface strain was applied, which is in sharp contrast to previous reports on Pt-based catalysts. Density functional theory calculations revealed that the characteristic strain-activity relationship of Pt{110} facets is the result of the counteraction of out-of-plane surface strain against the applied in-plane surface strain, which can effectively impose a tensile environment on the surface atoms of the Pd@Pt nanocrystals under the compressive in-plane strain.

Pt-based multimetallic nanocrystals (NCs) have attracted tremendous research interest because of their excellent catalytic properties in various electrocatalysis fields. However, the development of rational synthesis approaches that can give multimetallic NCs with desirable compositional structures is still a radical issue. In the present work, we devised an efficient strategy for the systematic control of the spatial distribution of constituent elements in Pt-based trimetallic core-shell NCs, through which NCs with distinctly different compositional structures, such as Au@PdPt, Au@Pd@Pt, AuPd@Pt, and AuPdPt@Pt core-shell NCs, could selectively be generated. The adjustment of the amount of a reducing agent, hydrazine, which can provide control over the relative reduction kinetics of multiple metals, is the key to the selective formation of NCs. Through extensive studies on the effect of the compositional structure of the trimetallic NCs on their catalytic function toward the methanol electro-oxidation reaction, we found that the Au@Pd@Pt NCs exhibited considerably enhanced catalytic performance in comparison to the other trimetallic NCs as well as to their binary counterparts, a commercial catalyst, and reported Pt-based nanocatalysts due to the optimized surface electronic structure. The present strategy will be useful to design and construct multicomponent catalytic systems for various energy and environmental applications.