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1. Preserving the shape of silver nanocubes under corrosive environment by covering their edges and corners with iridium

   https://doi.org/10.1039/d0nr05969b  

   Wang, Peng ; Ahn, Jaewan ; Gao, Ruoqi ; Qin, Dong ( October 2020 , Nanoscale)

   null (Ed.)

   Silver nanocubes have found use in an array of applications but their performance has been plagued by the shape instability arising from the oxidation and dissolution of Ag atoms from the edges and corners. Here we demonstrate that the shape of Ag nanocubes can be well preserved by covering their edges and corners with a corrosion-resistant metal such as Ir. In a typical process, we titrate a Na 3 IrCl 6 solution in ethylene glycol (EG) into a suspension of Ag nanocubes in an EG solution in the presence of poly(vinylpyrrolidone) (PVP) held at 110 °C. The Ir atoms derived from the reduction of Na 3 IrCl 6 by EG and Ag are deposited onto the edges and then corners for the generation of Ag–Ir core-frame nanocubes. Remarkably, our results indicate that a small amount of Ir atoms on the edges and corners is adequate to prevent the Ag nanocubes from transforming into nanospheres when heated in a PVP/EG solution up to 110 °C. We further demonstrate that these Ag–Ir nanocubes embrace plasmonic properties comparable to those of the original Ag nanocubes, making them immediately useful in a variety of applications. This strategy for stabilizing the shape of Ag nanocubes should be extendible to Ag nanocrystals with other shapes or nanocrystals comprised of other metals. 

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2. Breaking adsorption-energy scaling limitations of electrocatalytic nitrate reduction on intermetallic CuPd nanocubes by machine-learned insights

   https://doi.org/10.1038/s41467-022-29926-w  

   Gao, Qiang ; Pillai, Hemanth Somarajan ; Huang, Yang ; Liu, Shikai ; Mu, Qingmin ; Han, Xue ; Yan, Zihao ; Zhou, Hua ; He, Qian ; Xin, Hongliang ; et al ( April 2022 , Nature Communications)

   The electrochemical nitrate reduction reaction (NO₃RR) to ammonia is an essential step toward restoring the globally disrupted nitrogen cycle. In search of highly efficient electrocatalysts, tailoring catalytic sites with ligand and strain effects in random alloys is a common approach but remains limited due to the ubiquitous energy-scaling relations. With interpretable machine learning, we unravel a mechanism of breaking adsorption-energy scaling relations through the site-specific Pauli repulsion interactions of the metald-states with adsorbate frontier orbitals. The non-scaling behavior can be realized on (100)-type sites of ordered B2 intermetallics, in which the orbital overlap between the hollow *N and subsurface metal atoms is significant while the bridge-bidentate *NO₃is not directly affected. Among those intermetallics predicted, we synthesize monodisperse ordered B2 CuPd nanocubes that demonstrate high performance for NO₃RR to ammonia with a Faradaic efficiency of 92.5% at −0.5 V_RHEand a yield rate of 6.25 mol h⁻¹g⁻¹at −0.6 V_RHE. This study provides machine-learned design rules besides thed-band center metrics, paving the path toward data-driven discovery of catalytic materials beyond linear scaling limitations.

    

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3. Facet-selective deposition of Au and Pt on Ag nanocubes for the fabrication of bifunctional Ag@Au–Pt nanocubes and trimetallic nanoboxes

   https://doi.org/10.1039/c8nr01794h  

   Zhang, Zhiwei ; Ahn, Jaewan ; Kim, Junki ; Wu, Zhengyun ; Qin, Dong ( January 2018 , Nanoscale)

   We report a facile route to the synthesis of Ag@Au–Pt trimetallic nanocubes in which the Ag, Au, and Pt atoms are exposed at the corners, side faces, and edges, respectively. Our success relies on the use of Ag@Au nanocubes, with Ag 2 O patches at the corners and Au on the side faces and edges, as seeds for the site-selective deposition of Pt on the edges only in a reaction system containing ascorbic acid (H 2 Asc) and poly(vinylpyrrolidone). At an initial pH of 3.2, H 2 Asc can dissolve the Ag 2 O patches, exposing the Ag atoms at the corners of a nanocube. Upon the injection of the H 2 PtCl 6 precursor, the Pt atoms derived from the reduction by both H 2 Asc and Ag are preferentially deposited on the edges, leading to the formation of Ag@Au–Pt trimetallic nanocubes. We demonstrate the use of 2,6-dimethylphenyl isocyanide as a molecular probe to confirm and monitor the deposition of Pt atoms on the edges of nanocubes through surface-enhanced Raman scattering (SERS). We further explore the use of these bifunctional trimetallic nanoparticles with integrated plasmonic and catalytic properties for in situ SERS monitoring the reduction of 4-nitrothiophenol by NaBH 4 . Upon the removal of Ag via H 2 O 2 etching, the Ag@Au–Pt nanocubes evolve into trimetallic nanoboxes with a wall thickness of about 2 nm and well-defined openings at the corners. The trimetallic nanoboxes embrace plasmon resonance peaks in the near-infrared region with potential in biomedical applications. 

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4. Ag‐Enriched Ag‐Pd Bimetallic Nanoframes and Their Catalytic Properties

   https://doi.org/10.1002/cnma.201600080  

   Li, Jumei ; Sun, Xiaojun ; Qin, Dong ( May 2016 , ChemNanoMat)

   We report a facile synthesis of Ag‐enriched Ag‐Pd bimetallic nanoframes with ridges as thin as 1.7 nm. The synthesis involves co‐titration of aqueous AgNO₃and Na₂PdCl₄solutions into an aqueous suspension of Ag nanocubes at room temperature in the presence of ascorbic acid and poly(vinyl pyrrolidone). The Ag and Pd atoms derived from the co‐reduction by ascorbic acid are co‐deposited on the edge and corner sites of Ag nanocubes for the generation of Ag@Ag‐Pd core–frame nanocubes. When subjected to H₂O₂etching, the Ag cores are selectively removed to generate Ag‐Pd bimetallic nanoframes made of ultrathin ridges enriched in Ag. In comparison to both the Ag nanocubes and Ag@Ag‐Pd core‐frame nanocubes, the Ag‐Pd bimetallic nanoframes exhibit markedly enhanced activity in catalyzing the reduction of 4‐nitrophenol by NaBH₄.

    

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5. Pd‐Ru Alloy Nanocages with a Face‐Centered Cubic Structure and Their Enhanced Activity toward the Oxidation of Ethylene Glycol and Glycerol

   https://doi.org/10.1002/smtd.201900843  

   Zhao, Ming ; Lyu, Zhiheng ; Xie, Minghao ; Hood, Zachary D. ; Cao, Zhenming ; Chi, Miaofang ; Xia, Younan ( January 2020 , Small Methods)

   This article reports a facile method for the synthesis of Pd‐Ru nanocages by activating the galvanic replacement reaction between Pd nanocrystals and a Ru(III) precursor with I‐ions. The as‐synthesized nanocages feature a hollow interior, ultrathin wall of ≈2.5 nm in thickness, and a cubic shape. Our quantitative study suggests that the reduction rate of the Ru(III) precursor can be substantially accelerated upon the introduction of I‐ions and then retarded as the ratio of I‐/Ru³⁺is increased. The Pd‐Ru nanocages take an alloy structure, with the Ru atoms in the nanocages crystallized in a face‐centered cubic structure instead of the hexagonal close‐packed phase taken by bulk Ru. Using Pd nanocubes with different edge lengths, the dimensions of the nanocages in the range of 6−18 nm can readily be tuned. When tested as catalysts toward the electro‐oxidation of ethylene glycol and glycerol, respectively, the Pd‐Ru cubic nanocages prepared from 18 nm Pd cubes exhibit 5.1‐ and 6.2‐fold enhancements in terms of mass activity relative to the commercial Pd/C. After 1000 cycles of accelerated durability test, the mass activities of the nanocages are still 3.3 and 3.7 times as high as that of the pristine commercial Pd/C catalyst, respectively.

    

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