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We report the fabrication of PdSm bimetallic nanocrystals with controlled shapes and explore their applications as the electrocatalysts for electroxidation of ethanol (EOR) in alkaline medium. The success of current synthesis relies on the co-reduction of Pd(acac) 2 and Sm(acac) 3 in the presence of N-oleyl-1,3-propanediamine (OPDA) and Mo(CO) 6 at an elevated temperature. For the first time, ultrathin nanostructures composed of Pd-rare earth metal bimetals could be prepared in high purity, in the form of ultrathin porous nanosheets and concave tetrahedra, together with the size/edge length limited to sub-3 nm size range. When serving as electrocatalysts for EOR, the carbon-supported PdSm nanocrystals exhibited in seven-fold increase in mass activity as compared to that of Pt/C, as well as improved reaction kinetics and long-term durability. DFT calculations verify that the PdSm NCs/C catalyst modulate the reaction pathway of ethanol oxidation with lower energy barriers as compared with Pd catalyst, accounting for the improved catalytic performance. The present study provides a feasible strategy to create rare earth metal-doped bimetallic nanocrystals with controlled morphology for rational design over fuel cell catalysts and could be extended to other noble metals or alloys. Ultrathin Sm-doped Pd nanocrystals with two exotic shapes, ultrathin porous nanosheet and concave tetrahedron, are successfully prepared via a one-pot synthesis, exhibiting noticeable enhancement in electrocatalytic activity for ethanol oxidation reaction in alkaline medium. [Display omitted] • Sm-doped Pd nanocrystals were facilely synthesized with ultrathin sizes. • The morphologies of porous nanosheet and concave tetrahedron were obtained. • PdSm NCs/C exhibited enhanced EOR mass activity, reaction kinetics and stability. • DFT calculations suggest the Sm-doping can lower the energy barriers for EOR. [ABSTRACT FROM AUTHOR]

We report a niche route to the fabrication of Au-based hybrid nanostructures in the form of homojunction via seeded growth mediated with etching regrowth. In particular, the trioctahedral Au nanoparticles are initially doped with limited amounts of Pt/Ag atoms on the surface, followed by oxidative etching using HAuCl4. Instead of truncation on sharp corners/edges, the resulting products maintain the trioctahedral morphology but with an extra segment anchored on one side of the particle. Due to the structural advantages in metal–metal interface engineering and elemental doping, the current Au-based nanoscale homojunctions exhibit improved specific activity, reaction kinetics, and long-term durability in electrooxidation of methanol, as compared to pure Au trioctahedral counterparts. As verified by DFT simulation, such high catalytic performance can be ascribed to the favorable adsorption of the reactive species and low energy barrier for the rate determining step of Pt/Ag doping on the Au-Au interface. The present study introduces a niche synthetic strategy to create noble metal hybrid nanostructures based on oxidative etching and validates their promising use in electrocatalysis, which could be beneficial for the rational design of advanced fuel cell catalysts with versatile interface engineering. [ABSTRACT FROM AUTHOR]

Noble metal Janus nanocrystals involving components with the same crystal structure and close lattice constants are technically difficult to produce as anisotropic growth is not favored under general deposition conditions. Herein, taking Au and Ag, we describe a feasible synthetic strategy to create Au–Ag Janus nanoparticles (JNPs) with tunable sizes, which exhibit multiple plasmonic absorptions in the UV-vis range. The success of the current synthesis lies in the surface doping of trisoctahedral (TOH) Au seeds with limited amount of Pt/Ag atoms to introduce a relatively large lattice strain during the seeded growth, which is found crucial to facilitate the anisotropic deposition of Ag. In contrast, the use of undoped Au seeds leads to the formation of Au@Ag core–shell nanoparticles. The size of resulting products could be tuned by varying the amount of the added Ag precursor or the size/quantity of Au seeds. Compared to core–shell counterparts, the current Au–Ag Janus nanoparticles exhibit more plasmonic absorption peaks. Owing to such advantages, the current Au–Ag Janus nanoparticles show enhanced catalytic properties in the reduction of 4-nitrophenol under UV-vis light irradiation. The current study provides a feasible strategy that allows the fabrication of Janus bimetallic nanocrystals with elements having a close lattice constant and validates the promising use as plasmonic catalysts, which could be potentially extended to other metals or alloys. [ABSTRACT FROM AUTHOR]

Controlled synthesis of two-dimensional noble metal nanomaterials with an in-plane branching morphology has been of great research interest recently, but has so far achieved limited success for AuAg-based nanocrystals. Herein, we report the fabrication of gold–silver (AuAg) nanosheets with abundant in-plane cracking and sub-10 nm thickness via one-pot kinetics-controlled synthesis. In particular, the dropwise addition of Au/Ag precursor solutions into a mixture of octadecyltrimethylammonium chloride and ascorbic acid, kept in an ice–water bath, leads to the formation of nanobelts/nanowires initially, followed by their growth into branched nanosheets. These AuAg products can further convert to AuAgM (M = Pd or Pt) nanosheets via galvanic replacement reaction under ambient conditions. Interestingly, the AuAgPd nanosheets are obtained with a Au@PdAg core–shell elemental distribution with many zigzag edges. In contrast, the AuAgPt nanosheets show a homogeneous distribution of all three metals, together with a highly stippled surface. All these AuAg-based nanosheets exhibit strong absorbance in the near-infrared region and thus show superb activities as photocatalysts for UV-vis light-assisted reduction of 4-nitrophenol due to the effect of plasmon enhancement. The present study provides a feasible route to generating AuAg-based multimetallic nanocrystals with a two-dimensional structure, in-plane branching morphology, and effective control over the elemental distribution, which could be potentially extended to other noble metals and/or alloys for the rational design of plasmonic photocatalysts. [ABSTRACT FROM AUTHOR]

We report a niche synthetic strategy to manipulate the shape of gold‐silver (AuAg) nanocrystals based on kinetics control. The success of current work relies on the use of two syringe pumps to add Au and Ag precursor solutions independently at distinct injection rates, which allows the separate control over the feeding rate of Au and Ag atoms, respectively. Such strategy is validated effective in both one‐pot reduction and seeded growth involving spherical and rod‐likes Au seeds. By conducting orthogonal experiments setting two injection rates at three levels, a set of morphologies are obtained. Interestingly, AuAg alloy nanocrystals in the form of multipod, hollow protruded particles, and branched hollow nanoplate, that are rare to obtain via conventional routes, are successfully screened out, exhibiting the unique advantage of this strategy. The current work provides a feasible approach to applying kinetics control over AuAg bimetallic nanocrystals, which could be extended to other noble metals or material combinations. [ABSTRACT FROM AUTHOR]

We report a niche strategy to fabricate planar trimetallic nanocrystals with in‐plane branches and a unique hybrid structure. The success of current work relies on the use of seeded growth to produce Au@Ag core‐shell nanocubes, followed by the reaction with an excessive third metal precursor (i. e. Pd) via galvanic replacement reaction (GRR) in the presence of controlled reduction. The morphology of resulting products varied in the order of cube, concave cube, hollow cage, yolk‐shell frame, and finally branched nanoplates with Au‐PdAg hybrid structure. The controlled reduction involved in the GRR process, together with the use of Au seed at appropriate amounts and docosyltrimethylammonium chloride as the capping agent, is demonstrated to be crucial for the formation of such unique structure. When loaded on carbon black and working as electrocatalysts for electroxidation of ethanol in alkaline media, the current products exhibit satisfying electrocatalytic activity (e. g. 591 mA mgPd−1 in mass activity and 10.01 A m−2 in specific activity), improved kinetics, and long‐term durability, as compared to commercial Pt/C. The present study offers a feasible route to applying precise spatial control over elemental metals for two‐dimensional dendritic noble metal nanocrystals and could be potentially extended to other metals or alloy. [ABSTRACT FROM AUTHOR]

Etching and regrowth are two typical processes involved during wet-chemical synthesis of noble-metal nanocrystals. In the present study, we demonstrate that by rationally manipulating the two processes, trimetallic nanocrystals with a unique multilayered structure can be successfully prepared in high purity, as well as with tunable sizes. In particular, by conducting co-reduction of Pd and Pt precursors in the presence of spherical Au seeds, the continuous etching of Pt(IV) ions as enabled by insufficient reducing power, together with the regrowth of Au and Pd atoms during the growth stage, allows the resultant products to exhibit a multi-layered elemental distribution, where Pd and Pt are in the inner shell while Au and Pt are dominant in the outer shell. When supported on carbon and used as electrocatalysts, these AuPdPt multilayered nanodendrites with controlled sizes in the range of 32–88 nm show an improved electrocatalytic activity and long-term durability for formic acid oxidation, as compared to commercial Pt/C. The present study offers a facile method to prepare tri-metallic nanocrystals with a controlled shape and spatial elemental distribution, which could be further extended to other noble metals or alloys. [ABSTRACT FROM AUTHOR]

We report a seeded growth of gold (Au) nanoplates with two distinct morphologies, which are similar to a lotus leaf and a donut, respectively. The success of this synthesis relies on the use of flat Au nanoplates in high purity as seeds, followed by a controlled deposition. In particular, the presence of Ag+ led to the deposition of Au atoms preferentially occurred at the central part of one face of the nanoplate and thus the formation of lotus leaf‐like shape. In contrast, when Ag+ was absent, the growth mainly occurred to the edge region. Then, cold‐welding of newly‐formed branches and further diffusion of Au atoms created holes in the nanoplate, resulting in the formation of donut‐like shape. The Au nano‐lotus leaves with tunable sizes exhibited absorbance in near‐infrared region and enhanced chemical activities in electrochemical measurements. The current strategy is extended to fabricate Au−Ag nanoplates with a similar lotus leaf‐like morphology, which also exhibited strong absorbance in near‐infrared region in UV‐vis extinction spectra. The current work allows the fabrication of two‐dimensional Au‐based nanomaterials with concave shape and three‐dimensional architecture and could be potentially extended to other noble metals and alloys. [ABSTRACT FROM AUTHOR]

We report an ultrafast synthesis of wavy gold‐silver (AuAg) nanowires with tunable diameters via a seed‐mediated co‐reduction. The success of current strategy relies on the use of an elevated reaction temperature to accelerate the synthesis to be completed within several minutes and the use of Au seeds with controlled sizes to enable the manipulation over their diameters in the range of 2–10 nm. The presence of chloride‐contained quaternary ammonium surfactant and excessive reductant have been demonstrated to be critical for the high‐yield formation of AuAg products with the unique morphology of wavy nanowire. Due to the advantage in size control, the size effect on the plasmonic behavior of AuAg alloy wavy nanowires is investigated, where the products with sub‐5 nm diameter exhibit a broad shoulder absorbance peak in their spectrum. [ABSTRACT FROM AUTHOR]

Branched Au nanocrystals with sub-10-nm arms are synthesized via a one-pot reduction in aqueous phase. The success of current work relies on the use of octadecyltrimethylammonium chloride as the shape-directing capping agent to facilitate the formation of branched products in high purity. Their overall size could be controlled in the range of 16–60 nm by varying the Au precursor amount or concentration of capping agent, and the diameter of arms is limited to sub-10-nm size range. Interestingly, Au nanocrystals with a unique morphology, sheet-wrapped dendrites, could be obtained when the concentration of a reductant was varied. The current strategy is also validated effective in the fabrication of dendritic products composed of other noble metals or alloys in addition to Au by simply using the alternative metal precursor. As compared to spherical counterparts, the current branched Au nanocrystals exhibited noticeable red-shift in UV-Vis extinction spectrum and enhanced catalytic activities for electrooxidation of ethanol in alkaline media. [ABSTRACT FROM AUTHOR]

We report a facile synthesis of silver (Ag) nanoplates with rough edges via seeded growth. The key to this success is relies on the manipulation of the competitive relationship between surface diffusion and kinetics-controlled growth. In particular, Ag atoms initially deposit on the corners and edges of seed plates and then diffuse towards the low-curvature region in a controlled way to form edges with rough features. The as-prepared Ag plate-shaped products were also tested for surface enhanced Raman spectroscopy (SERS), which exhibited the dependence of SERS enhancement on edge roughness. The current work offers an effective synthetic route to control the shape of Ag nanoplates and could find important use in shape-controlled synthesis of other noble metals. [ABSTRACT FROM AUTHOR]