Bimetallic Alloy Nanostructures Research Articles

Boosting Pt utilization via strategic Co Integration: Structural and mechanistic investigation of High-Performance Pt-Co alloy nanocatalysts for catalytic benzene combustion

Platinum (Pt)-based catalysts exhibit notable efficacy in reducing emissions of hazardous volatile organic compounds (VOCs), such as benzene. Nevertheless, the high cost and limited availability of Pt necessitate exploring reasonable strategies to optimize Pt utilization and enhance catalytic efficiency. Thus, pressing needs emerge to develop efficient Pt-based catalysts. This study investigates the catalytic combustion of benzene utilizing an antimony-doped tin oxide (ATO) supported platinum-cobalt (Pt-Co) alloy catalyst. The incorporation of cobalt into Pt nanoparticles leads to Co atoms occupying bulk sites in the Pt-Co alloy, elevating the surface exposure of Pt atoms and enriching Pt on the surface, thereby providing additional active sites for catalysis. Advanced characterization techniques provide critical insights into the morphology, size distribution, crystallinity and valence states of Pt upon strategic Co alloying. Pt-Co/ATO exhibits exceptional low-temperature activity, achieving 95 % benzene conversion at 170 °C, which is 30 °C lower than the 200 °C required for Pt/ATO. Pressure-dependent kinetic analysis reveals a Langmuir-Hinshelwood mechanism involving the co-adsorption of benzene and oxygen reactants on active Pt-Co alloy sites. This study contributes insights into tuning bimetallic alloy nanostructures to optimize noble metal utilization and catalytic performance for VOC abatement, establishing a foundation for advancing sustainable emissions control technology.

Atomic coordination environment engineering of bimetallic alloy nanostructures for efficient ammonia electrosynthesis from nitrate

Electrochemical nitrate reduction reaction (NO3RR) to ammonia has been regarded as a promising strategy to balance the global nitrogen cycle. However, it still suffers from poor Faradaic efficiency (FE) and limited yield rate for ammonia production on heterogeneous electrocatalysts, especially in neutral solutions. Herein, we report one-pot synthesis of ultrathin nanosheet-assembled RuFe nanoflowers with low-coordinated Ru sites to enhance NO3RR performances in neutral electrolyte. Significantly, RuFe nanoflowers exhibit outstanding ammonia FE of 92.9% and yield rate of 38.68 mg h-1 mgcat-1 (64.47 mg h-1 mgRu-1) at -0.30 and -0.65 V (vs. reversible hydrogen electrode), respectively. Experimental studies and theoretical calculations reveal that RuFe nanoflowers with low-coordinated Ru sites are highly electroactive with an increased d-band center to guarantee efficient electron transfer, leading to low energy barriers of nitrate reduction. The demonstration of rechargeable zinc-nitrate batteries with large-specific capacity using RuFe nanoflowers indicates their great potential in next-generation electrochemical energy systems.

Thermally generated Au–Ag nanostructures with tunable localized surface plasmon resonance as SERS activity substrates

Various Au–Ag bimetallic alloy nanostructures were obtained as sensitive surface-enhanced Raman scattering (SERS) substrates by changing the thermal annealing sequence. The atomic force microscopy (AFM) and scanning electron microscopy (SEM) results confirm that Au/Ag bimetallic clusters and Ag–Au core-shell like structures can be designed by thermal annealing. The absorption spectra showed that the localized surface plasmon resonance (LSPR) frequency of the annealed Au/Ag bimetallic alloy structure could effectively shift from the near ultraviolet to the visible region. At the same time, the Au/Ag bimetallic alloy films modified by thermal annealing have shown satisfactory performance as SERS substrates. Raman enhancement mechanism of Au–Ag bimetallic alloy films is verified by finite-difference time-domain (FDTD) simulation results.

Effect of Capping Agent on the Shape and Catalytic Activity of PtPd Bimetallic Alloy Nanostructures

In this work, PtPd nanostructures have been synthesized via the chemical reduction method with different capping agents (i.e., PVA, PVP, and PEG), whilst the strong reducing agent, NaBH4, was used in this study to reduce the metal salt to zero-valent PtPd nanostructures. Both PtPd synthesized with PVP and PEG exhibit nanoparticle structures, whereas PtPd synthesized in PVA demonstrates large, interconnected network structures. Pt-Pd synthesized with PVP exhibits a high ECSA value of 692.68 m2/g compared to without capping agent (287.80 m2/g) indicating large active sites, which increases its catalytic function. This study concludes that the presence of a capping agent influences the morphological structure and the catalyst's efficiency in performing a redox reaction at the surface.

Catalytically active nanosized Pd9Te4 (telluropalladinite) and PdTe (kotulskite) alloys: first precursor-architecture controlled synthesis using palladium complexes of organotellurium compounds as single source precursors.

Several intermetallic binary phases of Pd–Te including Pd3Te2, PdTe, PdTe2, Pd9Te4, Pd3Te, Pd2Te, Pd20Te7, Pd8Te3, Pd7Te2, Pd7Te3, Pd4Te and Pd17Te4 are known, and negligible work (except few studies on PdTe) has been done on exploring applications of such phases and their fabrication at nanoscale. Hence, Pd(ii) complexes Pd(L1)Cl2 and Pd(L2-H)Cl (L1): Ph–Te–CH2–CH2–NH2 and L2: HO–2-C6H4–CH Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N–CH2CH2–Te–Ph were synthesized. Under similar thermolytic conditions, complex Pd(L1)Cl2 with bidentate coordination mode of ligand provided nanostructures of Pd9Te4 (telluropalladinite) whereas Pd(L2-H)Cl with tridentate coordination mode of ligand yielded PdTe (kotulskite). Bimetallic alloy nanostructures possess high catalytic potential for Suzuki coupling of aryl chlorides, and reduction of 4-nitrophenol. They are also recyclable upto six reaction cycles in Suzuki coupling.

Selective Reduction Sites on Commercial Graphite Foil for Building Multimetallic Nano‐Assemblies for Energy Conversion

AbstractSelective reduction sites are important for systematically building alloy nanostructure assemblies on various substrates. Utilizing a galvanic exchange protocol, in the present study, multimetallic alloy‐type nanostructures were developed on selective reduction sites, which were found to exist on the edges of a commercial graphite foil. Notably, the evaluated method is environmentally friendly and involves sustainable techniques. It was determined that a ternary alloy nanostructure on graphite, consisting of Au, Pd, and Ni, exhibits superior catalytic activity toward ethanol electro‐oxidation reaction in an alkaline medium in comparison to the corresponding unimetallic or bimetallic alloy nanostructures. Correspondingly, a bimetallic Fe and Ni‐based alloy material on graphite was shown to display improved oxygen evolution reaction response.

Air-stable magnetic cobalt-iron (Co7Fe3) bimetallic alloy nanostructures via co-digestive ripening of cobalt and iron colloids

Phase pure Co7Fe3 alloy magnetic nanostructures were successfully synthesized by co-digestive ripening of Fe/Co-toluene nanoparticles in mesitylene in the presence of hexadecyl amine (HDA). Controlled heat treatment of as-synthesized samples under anaerobic conditions showed a transformation of disordered-to-ordered crystal structure, which was confirmed by PXRD and TEM measurements. This also resulted in carbonization of HDA over the nanoparticles surface rendering them air-stable. Magnetic measurements of these carbon-encased samples revealed enhanced saturation magnetization (MS) values compared to the as-prepared samples. The zero field cooling (ZFC) and field cooling (FC) curves demonstrated that Co7Fe3 nanoparticles exhibit ferromagnetic behaviour at room temperature. These air-stable Co–Fe magnetic nanostructures have immense potential for applications as soft magnets.

Enhanced Catalytic Performance for Hydrogenation of Substituted Nitroaromatics over Ir-Based Bimetallic Nanocatalysts.

IrM (M = Fe, Co, and Ni) alloy nanoparticles (NPs) were synthesized in a solution by employing butyllithium as a reduction agent and oleylamine as a stabilizing agent, and the alumina-supported IrM bimetallic nanoparticles were tested for selective hydrogenation of various substituted nitroaromatics. The relevant characterizations including X-ray diffraction, X-ray photoelectron spectra, transmission electron microscopy, and diffuse reflectance fourier transform infrared with CO probes confirm that IrM NPs are uniform alloys. The obtained IrM/Al2O3 catalysts show significantly enhanced catalytic activity as well as selectivity relative to individual monometallic Ir catalysts, indicating a unique catalytic property of bimetallic alloy nanostructures. Among these bimetallic catalysts, IrNi/Al2O3 illustrate the highest activity and selectivity for hydrogenation of various substituted nitroaromatics. Calculations by density functional theory suggest that bimetallic structures of IrNi facilitate the reactant adsorption and product desorption, resulting in enhanced catalytic performance.

One-pot green synthesis of bimetallic hollow palladium-platinum nanotubes for enhanced catalytic reduction of p-nitrophenol

Bimetallic alloy nanostructures have garnered much attention due to their unique performances in catalytic processes. However, decline in catalytic activity over the life span has been a protracted limitation, ascribed largely to the aggregation or dissociation of particles and still remains a challenge for manufacturing bimetallic nanostructures of sufficient stability. Herein, a surfactant- and solvent-free greener strategy is presented for the fabrication of bimetallic palladium-platinum (PdPt) nanotubes (NTs), deploying lipid tubules as template and ascorbic acid as a reducing agent; the ensuing NTs comprise crystalline tubal nanostructures of ∼12 μm length, ∼500 nm cross-sectional diameter, and ∼57 nm tube wall thickness. When used for the catalytic reduction of p-nitrophenol (PNP), the PdPt NTs delivered improved kinetic apparent rate constants (kapp) compared to Pt NTs (0.5 min−1vs. 0.2 min−1). Moreover, the NTs demonstrated high stability when used over multiple catalytic cycles thus opening up new potential routes for the fabrication of alloy NTs using lipid tubules as templates.

Platinum-Copper Bimetallic Alloy Nanoflowers as Efficient Electrocatalyst for the Methanol Oxidation Reaction.

Special morphological noble metal-based bimetallic alloy nanostructures became popular for methanol oxidation reaction in order to reduce the high cost of the Pt catalyst and improve the catalyst activity. Herein, we developed a facile one pot hydrothermal method for the synthesis of platinum-copper bimetallic nanoflowers (Pt-Cu NFs) in the presence of hexadecyl trimethyl ammonium bromide (CTAB). The morphology, structure and composition of Pt-Cu NFs were carefully characterized and the synthesized parameters were optimized systematically by adjusting different experimental conditions. Results showed that the CTAB usage and the NaI amount were critical to the controlled synthesis of Pt-Cu NFs. The Pt-Cu NFs were high-performance electrocatalysts for the methanol oxidation reaction (MOR) with superior activity and superior stability in alkaline solution, which were far better than pure Pt nanoparticle electrocatalysts.

Polyelectrolyte-assisted soft reduced process for Pt-Cu nanoclusters with enhanced electrocatalytic activity for the methanol oxidation reaction

Noble metal-based bimetallic alloy nanostructures became popular for methanol oxidation reaction (MOR) in order to lower the high cost of the Pt catalyst and improve the catalyst activity as well as their CO tolerance. Fabrication of the secondary structures of bimetallic alloy nanocrystal clusters is desired due to their abundant accessible active sites and enhanced stability. Herein, for the first time, we prepared novel Pt-Cu bimetallic alloy nanocrystal clusters (Pt-Cu BANCs) in the presence of poly(diallyldimethylammonium chloride) (PDDA). The selective use of PDDA and control of the amount of PDDA are critical to the controlled fabrication of secondary structures with nanograins assembled together. The Pt-Cu BANCs offered abundant active sites available and enhanced durable stability, and are investigated to be high-performance electrocatalysts for MOR (i.e. the ECSAs of Pt-Cu BANCs and the specific current density of methanol oxidation on Pt-Cu BANCs are 73.9 m2/g and 3.36 mA·cm-2, respectively), which are far better than those of commercial Pt/C and Pt black. Our results reported herein developed an effective strategy of polyelectrolyte-assisted soft reduced process for the creation of the secondary structures of bimetallic alloy nanocrystal clusters, which would be used as enhanced catalysts in the field of clean energy.

Biogenic synthesis of shape-tunable Au-Pd alloy nanoparticles with enhanced catalytic activities

Herein, we report the synthesis of bimetallic Au-Pd and monometallic Au and Pd nanoparticles (NPs) by successive reduction of the respective metal ions using phytochemicals in the form of plant extract under ambient conditions. Phytochemicals act both as reducing and shape directing agent for metal and alloy NPs. The synthesized nanostructures were characterized by different microscopic, spectroscopic and diffractometric techniques. Microscopic results confirmed that the shape and size of the alloy nanostructures can be tuned by varying the concentration ratio of metal ions in the reaction medium. Energy dispersive X-ray and X-ray photoelectron spectroscopic analysis confirmed the formation of bimetallic Au-Pd nanostructures. The purity and crystalline properties were studied by X-ray diffraction technique. UV–vis spectra were recorded to study the optical properties of the synthesized nanostructures. Further, we tested the catalytic activity of both the monometallic and bimetallic alloy nanostructures in borohydride reduction of hazardous organic dye molecules in aqueous medium. The bimetallic alloy NPs exhibit better catalytic activities compared to their respective monometallic nanoparticles.

Synthesis of shape and size-dependent CuAg bimetallic dumbbell structures for organic pollutant hydrogenation

Combining silver and copper is a good way to decrease the cost of silver and the instability of copper. Bimetallic nanomaterials have emerged as effective catalysts with chemical and physical properties distinct from those of discrete metals. In this study, we develop a method for synthesis of CuAg bimetallic alloy nanostructures of different sizes and shapes without the need for laborious conditions or toxic agents. Therefore, it is a fast, effective, and green chemical method for synthesizing active bimetallic alloy catalysts. The prepared nanostructures were fundamentally analyzed by UV–Vis spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, field emission transmission electron microscopy, and X-ray photoelectron spectroscopy. The catalytic activities of the prepared CuAg bimetallic nanostructures were investigated for the hydrogenation of aromatic nitro compounds, such as 4-nitrophenol, methylene blue, and methyl orange in the presence of NaBH4 in an aqueous medium.

ChemInform Abstract: Recent Advances in the Synthesis and Electrocatalytic Applications of Platinum‐Based Bimetallic Alloy Nanostructures

AbstractReview: 160 refs.

Recent Advances in the Synthesis and Electrocatalytic Applications of Platinum‐Based Bimetallic Alloy Nanostructures

AbstractPt‐based bimetallic alloy nanomaterials with a low Pt loading can exhibit promising catalytic properties with exciting electrochemical applications. An effective structure control of Pt‐based bimetallic alloy nanomaterials is critical to achieve enhanced catalytic properties. This review article focuses on recent advances in the controllable synthesis and electrocatalytic applications of Pt‐based bimetallic alloy nanostructures. Recent contributions on the controllable synthesis of a rich variety of Pt‐based bimetallic alloy nanostructures, for example, PtPd, PtCu, PtNi, PtCo, and PtFe, and hybrid nanostructures based on Pt‐based bimetallic alloy nanomaterials are summarized. Different Pt‐based bimetallic alloy nano‐electrocatalysts with enhanced activity and durability for different electrocatalytic reactions, such as the fuel cell reaction and the hydrogen evolution reaction, are outlined. Finally, an outlook on future trends and developments is provided.

Controllable galvanic synthesis of triangular Ag-Pd alloy nanoframes for efficient electrocatalytic methanol oxidation.

Triangular Ag-Pd alloy nanoframes were successfully synthesized through galvanic replacement by using Ag nanoprisms as sacrificial templates. The ridge thickness of the Ag-Pd alloy nanoframes could be readily tuned by adjusting the amount of the Pd source during the reaction. These obtained triangular Ag-Pd alloy nanoframes exhibit superior electrocatalytic activity for the methanol oxidation reaction as compared with the commercial Pd/C catalyst due to the alloyed Ag-Pd composition as well as the hollow-framed structures. This work would be highly impactful in the rational design of future bimetallic alloy nanostructures with high catalytic activity for fuel cell systems.

Triangular Ag-Pd alloy nanoprisms: rational synthesis with high-efficiency for electrocatalytic oxygen reduction.

We report the generation of triangular Ag-Pd alloy nanoprisms through a rationally designed synthetic strategy based on silver nanoprisms as sacrificial templates. The galvanic replacement between Ag nanoprisms and H2PdCl4 along with co-reduction of Ag(+)/Pd(2+) is responsible for the formation of final prismatic Ag-Pd alloy nanostructures. Significantly, these Ag-Pd alloy nanoprisms exhibited superior electrocatalytic activity for the oxygen reduction reaction (ORR) as compared with the commercial Pd/C catalyst. Such a high catalytic activity is attributed to not only the alloyed Ag-Pd composition but also the dominant {111} facets of the triangular Ag-Pd nanoprisms. This work demonstrates the rational design of bimetallic alloy nanostructures with control of selective crystal facets that are critical to achieve high catalytic activity for fuel cell systems.

Platinum-Based Oxygen Reduction Electrocatalysts

An efficient oxygen reduction reaction (ORR) offers the potential for clean energy generation in low-temperature, proton-exchange membrane fuel cells running on hydrogen fuel and air. In the past several years, researchers have developed high-performance electrocatalysts for the ORR to address the obstacles of high cost of the Pt catalyst per kilowatt of output power and of declining catalyst activity over time. Current efforts are focused on new catalyst structures that add a secondary metal to change the d-band center and the surface atomic arrangement of the catalyst, altering the chemisorption of those oxygencontaining species that have the largest impact on the ORR kinetics and improving the catalyst activity and cost effectiveness. This Account reviews recent progress in the design of Pt-based ORR electrocatalysts, including improved understanding of the reaction mechanisms and the development of synthetic methods for producing catalysts with high activity and stability. Researchers have made several types of highly active catalysts, including an extended single crystal surface of Pt and its alloy, bimetallic nanoparticles, and self-supported, low-dimensional nanostructures. We focus on the design and synthetic strategies for ORR catalysts including controlling the shape (or facet) and size of Pt and its bimetallic alloys, and controlling the surface composition and structure of core-shell, monolayer, and hollow porous structures. The strong dependence of ORR performance on facet and size suggests that synthesizing nanocrystals with large, highly reactive {111} facets could be as important, if not more important, to increasing their activity as simply making smaller nanoparticles. A newly developed carbon-monoxide (CO)-assisted reduction method produces Pt bimetallic nanoparticles with controlled facets. This CO-based approach works well to control shapes because of the selective CO binding on different, low-indexed metal surfaces. Post-treatment under different gas environments is also important in controlling the elemental distribution, especially the surface composition and the core-shell and bimetallic alloy nanostructures. Besides surface composition and facet, surface strain plays an important role in determining the ORR activity. The surface strain depends on the crystal size, the presence of an interface-lattice mismatch or twinned boundary, and between nanocrystals and extended single crystal surfaces, all of which may be factors in metal alloys. Since the common, effective reaction pathway for the ORR is a four-electron process and the surface binding of oxygen-containing species is typically the limiting step, density functional theory (DFT) calculation is useful for predicting the ORR performance over bimetallic catalysts. Finally, we have noticed there are variations among the published values for activity and durability of ORR catalysts in recent papers. The differences are often due to the data quality and protocols used for carrying out the analysis using a rotating disk electrode (RDE). Thus, we briefly discuss some practices used in such half-cell measurements, such as sample preparation and measurement, data reliability (in both kinetic current density and durability measurement) and iR correction that could lead to more consistency in measured values and in evaluating catalyst performances.

Solvothermal synthesis of Pt–Pd alloys with selective shapes and their enhanced electrocatalytic activities

Pt-Pd bimetallic alloy nanostructures with highly selective morphologies such as cube, bar, flower, concave cube, and dendrite have been achieved through a facile one-pot solvothermal synthesis. The effects of shape-controllers (sodium dodecyl sulfate (SDS), ethylenediamine-tetraacetic acid disodium salt (EDTA-2Na), NaI) and solvents (water/DMF) on the morphologies were systematically investigated. The electrocatalytic activities of these Pt-Pd alloy nanostructures toward formic acid oxidation were tested. The results indicated that these alloy nanocrystals exhibited enhanced and shape-dependent electrocatalytic activity toward formic acid oxidation compared to commercial Pt black and Pt/C catalysts.

Design of AgM Bimetallic Alloy Nanostructures (M = Au, Pd, Pt) with Tunable Morphology and Peroxidase-Like Activity

Bimetallic alloy nanoparticles (NPs) exhibit unique optical and catalytic properties that are dependent on their morphology and composition. In this paper, a general and facile way was developed to prepare Ag-related bimetallic alloy NPs with hollow/porous structures, including AgAu, AgPd, and AgPt. The formation of the alloy structures is evidenced by high-resolution transmission electron microscopy (TEM), scanning transmission electron microscopy−energy-dispersive X-ray analysis (STEM-EDX) mapping, and ultraviolet−visible−near-infrared (UV−vis−NIR) absorption spectra. AgM alloy NPs exhibit peroxidase-like activity. A unique composition dependence is found and can be used to tailor the catalytic activity. In addition to the recent discoveries about peroxidase mimetics on Fe3O4 NPs and sheetlike FeS nanostructures, our findings suggest a new type of candidate as peroxidase mimics. Furthermore, for noble metals, apart from size and shape, tailoring the composition poses another effective way to tune the catalytic activity.