Synthesis and Characterization of Ru Cubic Nanocages with a Face-Centered Cubic Structure by Templating with Pd Nanocubes

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• 作者：Ming Zhao ; Legna Figueroa-Cosme ; Ahmed O. Elnabawy ; Madeline Vara ; Xuan Yang ; Luke T. Roling ; Miaofang Chi ; Manos Mavrikakis ; Younan Xia
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：August 10, 2016
• 年：2016
• 卷：16
• 期：8
• 页码：5310-5317
• 全文大小：488K
• 年卷期：0
• ISSN：1530-6992

文摘

Nanocages have received considerable attention in recent years for catalytic applications owing to their high utilization efficiency of atoms and well-defined facets. Here we report, for the first time, the synthesis of Ru cubic nanocages with ultrathin walls, in which the atoms are crystallized in a face-centered cubic (fcc) rather than hexagonal close-packed (hcp) structure. The key to the success of this synthesis is to ensure layer-by-layer deposition of Ru atoms on the surface of Pd cubic seeds by controlling the reaction temperature and the injection rate of a Ru(III) precursor. By selectively etching away the Pd from the Pd@Ru core–shell nanocubes, we obtain Ru nanocages with an average wall thickness of 1.1 nm or about six atomic layers. Most importantly, the Ru nanocages adopt an fcc crystal structure rather than the hcp structure observed in bulk Ru. The synthesis has been successfully applied to Pd cubic seeds with different edge lengths in the range of 6–18 nm, with smaller seeds being more favorable for the formation of Ru shells with a flat, smooth surface due to shorter distance for the surface diffusion of the Ru adatoms. Self-consistent density functional theory calculations indicate that these unique fcc-structured Ru nanocages might possess promising catalytic properties for ammonia synthesis compared to hcp Ru(0001), on the basis of strengthened binding of atomic N and substantially reduced activation energies for N₂ dissociation, which is the rate-determining step for ammonia synthesis on hcp Ru catalysts.