Hexoctahedral Au Nanocrystals with High-Index Facets and Their Optical and Surface-Enhanced Raman Scattering Properties

Au nanocrystals (NCs) with an unprecedented hexoctahedral structure enclosed exclusively by high-index {321} facets have been prepared for the first time. Manipulating the NC growth kinetics by controlling the amount of reductant and the reaction temperature in the presence of a suitable surfactant was the key synthetic lever for controlling the morphology of the Au NCs. The hexoctahedral Au NCs exhibited efficient optical and surface-enhanced Raman scattering activities due to their unique morphological characteristics

One-Step Synthesis of Au@Pd Core−Shell Nanooctahedron

One-Step Synthesis of Au@Pd Core−Shell Nanooctahedro

One-Pot Synthesis of Monodisperse 5 nm Pd–Ni Nanoalloys for Electrocatalytic Ethanol Oxidation

Highly monodisperse 5 nm Pd–Ni alloy nanoparticles (NPs) were prepared by the reduction of Pd­(acac)₂/Ni­(acac)₂ mixtures with tert-butylamine-borane complex (TBAB) in the presence of oleic acid (OA) and oleylamine (OAm). Employing TBAB as an effective reductant and OA/OAm combination as an effective stabilizing agent is crucial to the formation of monodisperse Pd–Ni NPs. Experimental results collectively verify that the Pd–Ni alloy NPs form through the sequential nucleation-interdiffusion process and the simultaneous reduction of both metal precursors by the one-pot protocol is the key to the formation of homogeneous NPs. The Pd–Ni NPs were well-dispersed on carbon supports and chemically dealloyed after acetic acid washing through the selective dissolution of the less noble Ni component. The Pd–Ni NP catalysts exhibited much higher electrocatalytic activity and stability for ethanol oxidation than those of a commercial Pd/C catalyst

Multimetallic Alloy Nanotubes with Nanoporous Framework

One-dimensional nanotubes (NTs) that consist of multiple metallic components are promising platforms for potential applications, whereas only a few synthetic methods of multimetallic NTs have been reported to date. In the present work, we developed a general synthesis route for the production of uniform multicomponent one-dimensional tubular nanostructures with various combinations of Pt, Pd, and Ag by using ZnO nanowires (NWs) as sacrificial templates. The ZnO NWs serve not only as physical templates but also as nucleation sites for the reduction of metal precursors, and thereby several metal precursors could be reduced simultaneously to produce multimetallic NTs. By using this approach, Pt–Pd, Pt–Ag, and Pd–Ag binary alloy NTs, and even Pt–Pd–Ag ternary alloy NTs could be successfully prepared. The prepared Pt–Pd binary alloy NTs exhibited improved electrocatalytic activity and stability toward ethanol oxidation due to their characteristic tubular morphology with well-interconnected nanoporous framework and synergism between two constituent metals. Furthermore, our approach can facilitate the fabrication of patterned multimetallic NT arrays on solid and flexible substrates with strong mechanical robustness. The present templating method does not require any extra steps to remove templates or additional surfactants which are often required to control the shape of nanostructures. This strategy offers a convenient, versatile, low-cost, and highly valuable approach to the fabrication of multimetallic nanostructures with various components and compositions

One-Pot Synthesis of Ternary Alloy Hollow Nanostructures with Controlled Morphologies for Electrocatalysis

The rational design and synthesis of multimetallic hollow nanostructures (HNSs) have been attracting great attention due to their structural and compositional advantages for application in electrocatalysis. Herein, the one-pot synthesis of Pd–Pt–Ag ternary alloy HNSs with controllable morphologies through a self-templating approach without any pre-synthesized templates is reported. Simultaneous reduction of multiple metal precursors by ascorbic acid in the presence of cetyltrimethylammonium chloride (CTAC) yielded initially metastable Pd–Ag nanocrystals, which can act as a self-template, and subsequent galvanic replacement and reduction led to the formation of final Pd–Pt–Ag HNSs. The size and hollowness (the ratio of inner cavity diameter to outer diameter) of the HNSs could be tuned through control over the concentration of CTAC. This can be attributed to the manipulated reduction kinetics of multiple metal precursors with the change in the CTAC concentration. The prepared Pd–Pt–Ag HNSs exhibited improved catalytic performance for ethanol electro-oxidation due to their large active surface areas and ternary alloy composition

Regulating the Catalytic Function of Reduced Graphene Oxides Using Capping Agents for Metal-Free Catalysis

Reduced graphene oxide (rGO) functionalized with organic capping agents has gained increasing attention as a promising metal-free catalyst. To optimize the properties of rGO for target applications, comprehending the link between the catalytic function of rGO and the chemical and structural characteristics of capping agents is critical. Herein, we report a systematic study on the effect of capping agents on the catalytic function of rGO for redox reactions using nitrogen-containing surface modifiers with distinctly different chemical structures, such as poly­(diallyldimethylammonium chloride), cetyltrimethylammonium chloride, and poly­(allylamine hydrochloride), which have the capability to endow rGO with improved suspension stability, enhanced reactant adsorption, and modified electronic properties. Functionalized rGOs were facilely prepared by the reduction of graphene oxide with hydrazine in the presence of the capping agents. The results of model redox reactions, that is, 4-nitrophenol and ferricyanide reduction reactions, catalyzed by the functionalized rGOs corroborated that the way the capping agents functionalize rGO, which is highly correlated with their chemical structure, drastically influences the overall reaction kinetics, including induction time, reduction rate, total reaction time, and reaction order. This strongly suggests that the judicious selection of capping agents is crucial to fully harness the catalytic function of rGO and thus to design novel rGO-based non-metallic catalysts with controllable reaction kinetics

One-Pot Synthesis of Trimetallic Au@PdPt Core–Shell Nanoparticles with High Catalytic Performance

The development of an efficient synthesis method to produce multimetallic nanoparticles (NPs) with a desirable structure is strongly required to clarify the structure–composition–property relationship of NPs and to investigate their possible applications. However, the controlled synthesis of NPs consisting of multiple (n ≥ 3) noble metal components has been relatively unexplored in comparison to bimetallic NPs. In the present work, we have demonstrated a facile one-pot aqueous approach for the controlled synthesis of trimetallic Au@PdPt core–shell NPs with a well-defined octahedral Au core and a highly crystalline dendritic Pd–Pt alloy shell (Auoct@PdPt NPs). The simultaneous reduction of multiple metal precursors with dual reducing agents, namely, ascorbic acid and hydrazine, gave a fine control over the nucleation and growth kinetics of NPs, resulting in the formation of novel Auoct@PdPt NPs. The prepared NPs showed excellent catalytic performance for methanol electrooxidation, which can be attributed to their optimized binding strength toward adsorbate molecules due to the improved charge transfer between core and shell of the NPs. The present strategy can offer a convenient and valuable way to fabricate multicomponent nanostructures with desired structures and functions

Core–Shell Engineering of Pd–Ag Bimetallic Catalysts for Efficient Hydrogen Production from Formic Acid Decomposition

To develop high-performance bimetallic catalysts, fine control over both the ligand and strain effects of secondary elements on the catalytic function of primary elements is crucial. Here we introduce an approach to produce Pd–Ag bimetallic core–shell nanocatalysts with synergistic regulation of the ligand and strain effects of Ag. Through precise core–shell engineering, (PdAg alloy core)@(ultrathin Pd shell) nanocrystals with controlled core compositions and shell thicknesses in addition to a well-defined octahedral morphology could be realized. The prepared octahedral PdAg@Pd core–shell nanocrystals exhibited pronounced catalytic performance toward hydrogen production from formic acid decomposition. The maximum catalytic activity was achieved with PdAg@Pd nanocrystals consisting of PdAg alloy cores with an average Pd/Ag atomic ratio of 3.5:1 and 1.1 atomic layer of Pd shells, which showed a record high turnover frequency of 21 500 h–1 at 50 °C. This catalytic function could be attributed to the optimized combination of the electronic promotion and lattice strain effects of Ag on Pd. We envision that the present work can provide a rational guideline for the design of improved catalysts for various important chemical and electrochemical reactions

Polyhedral Au Nanocrystals Exclusively Bound by {110} Facets: The Rhombic Dodecahedron

Polyhedral Au Nanocrystals Exclusively Bound by {110} Facets: The Rhombic Dodecahedro

Enhancing Bifunctional Catalytic Activity via a Nanostructured La(Sr)Fe(Co)O_3−δ@Pd Matrix as an Efficient Electrocatalyst for Li–O₂ Batteries

One of the important challenges with a bifunctional electrocatalyst is reducing the large overpotential involved in the slow kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) at the air electrode in a metal–air redox battery. Here, we present a nanostructured LSCF@Pd matrix of nanostructured LSCF (Nano-LSCF) with palladium to enhance the bifunctional catalytic activity in Li–O2 battery applications. Pd nanoparticles can be perfectly supported on the surface of the Nano-LSCF, and the ORR catalytic activity was properly improved. When Nano-LSCF@Pd was applied to a cathode catalyst in Li–O2 batteries, the first discharge ability (16912 mA h g–1) was higher than that of Nano-LSCF (6707 mA h g–1) and the cycling property improved. These results demonstrate that the Pd-deposited nanostructured perovskite is a capable catalyst to enhance the ORR activity of LSCF as a promising bifunctional electrocatalyst